Petrophysical Reservoir by mohammedhusseiny

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									RHUM FIELD
RHUM PETROPHYSICAL RESERVOIR
EVALUATION




Simon Kay


July 2002




BP Exploration Operating Company Limited                                    MNS Developments
Dyce, Aberdeen                                                                           v1.0
E:\BACK UP\SCAN\Petrophysics\Rhum Petrophysical Reservoir Evaluation .doc         13/08/2005
                                           RHUM FIELD

        RHUM PETROPHYSICAL RESERVOIR
                 EVALUATION

                                                    SIMON KAY



                                                        July 2002




BP Exploration Operating Company Limited                                    MNS Developments
Dyce, Aberdeen                                                                           v1.0
E:\BACK UP\SCAN\Petrophysics\Rhum Petrophysical Reservoir Evaluation .doc         13/08/2005
                                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005


                                                          TABLE OF CONTENTS

      List of Figures
      List of Tables
      List of Enclosures
1.     EXECUTIVE SUMMARY............................................................................................................... 4

2.     INTRODUCTION AND SCOPE..................................................................................................... 7

       2.1.      Workscope ........................................................................................................................ 7
       2.2.      Depth Conventions............................................................................................................ 8
3.     FIELD AND WELL DATABASE..................................................................................................... 9

4.     FIELD TEMPERATURE AND PRESSURE ................................................................................ 11

5.     WELL – BY – WELL EVALUATION ............................................................................................ 13

       5.1.      3/29a – 4 Review ............................................................................................................ 13
                 5.1.1. 3/29a – 4 Data .................................................................................................. 13
                 5.1.2. Review of PGL Analysis.................................................................................... 14
                      5.1.2.1. Environmental Corrections ..................................................................... 14
                      5.1.2.2. Shale Volume (VSH) .............................................................................. 15
                      5.1.2.3. Effective Porosity (PHIE) ........................................................................ 15
                      5.1.2.4. Water Saturation (SW) ........................................................................... 15
                 5.1.3. MRIL Processing............................................................................................... 15
                 5.1.4. New Petrophysical Analysis.............................................................................. 16
                      5.1.4.1. Environmental Corrections ..................................................................... 16
                      5.1.4.2. Analysis .................................................................................................. 16
                      5.1.4.3. VSH ........................................................................................................ 16
                      5.1.4.4. PHIE ....................................................................................................... 18
                      5.1.4.5. SW .......................................................................................................... 20
       5.2.      3/29a – 2 Review ............................................................................................................ 21
                 5.2.1. New Petrophysical Analysis.............................................................................. 21
                      5.2.1.1. VSH ........................................................................................................ 21
                      5.2.1.2. PHIE ....................................................................................................... 21
                      5.2.1.3. SWE........................................................................................................ 21
                      5.2.1.4. Lower Reservoir Section ........................................................................ 21
6.     LITHOLOGY ANALYSIS ............................................................................................................. 23

       6.1.      Methodology.................................................................................................................... 23
       6.2.      Validation......................................................................................................................... 25
7.     PERMEABILITY ANALYSIS........................................................................................................ 27

8.     PRESSURE ANALYSIS AND FREE WATER LEVEL ................................................................ 31

9.     SATURATION-HEIGHT FUNCTIONS ........................................................................................ 35

10.              ZONE AVERAGES ......................................................................................................... 37

11.              RHUM ROCK PROPERTIES.......................................................................................... 38

12.              CONCLUSIONS AND RECOMMENDATIONS............................................................... 39

13.              REFERENCES................................................................................................................ 40




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                                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005


List of Figures

Figure 1.1.        3/29 – 2 Rhum Well Summary – Reservoir Section ................................................ 5
Figure 1.2.        3/29a – 4 Rhum Well Summary – Reservoir Section .............................................. 6
Figure 2.1.        Rhum Field Location Map.......................................................................................... 8
Figure 4.1.        3/29a – 4: Temperature Gradient used in Log Analysis ....................................... 11
Figure 4.2.        Rhum Field Formation Pressures........................................................................... 12
Figure 5.1.        GR Response Histograms ....................................................................................... 17
Figure 5.2.        3/29a – 4 Core Porosity vs Log Density Crossplot in the Gas Leg ..................... 19
Figure 6.1.        GR vs Depth Plot: 3/29 – 2 & 3/29a – 4. .................................................................. 24
Figure 6.2.        RHOB vs Depth Plot: 3/29 – 2 & 3/29a – 4.............................................................. 24
Figure 6.3.        Crossplot – RHO_MAA vs U_MAA: 3/29a – 4 Reservoir ...................................... 24
Figure 6.4.        Crossplot – PHIT vs RHO_MAA: 3/29 – 2 and 3/29a – 4 Reservoir...................... 24
Figure 6.5.        RHOB Histogram: 3/29 – 2 & 3/29a – 4. .................................................................. 25
Figure 6.6.        RHO_MAA vs VSH Cross Plot: 3/29 – 2 & 3/29a – 4.............................................. 25
Figure 6.7.        3/29a – 4 UMR2 Zone Log Resolution .................................................................... 26
Figure 7.1.        3/29 – 2 Poroperm Relationship.............................................................................. 28
Figure 7.2.        3/29a – 4 Poroperm Relationship............................................................................ 29
Figure 7.3.        3/29a – 4 Log Permeability Compared with Core Permeability ........................... 30
Figure 8.1.        3/29a – 4: RCI and FMT Formation Pressure Plot ................................................. 32
Figure 8.2.        Rhum Field Formation Pressure Plot ..................................................................... 33
Figure 8.3.        Well Corellation in True Vertical Depth Indicating FWL Position in Reservoir.. 34
Figure 9.1.        3/29a – 4 Sw – Height Functions............................................................................. 36


List of Tables

Table 3.1. Rhum Field Data............................................................................................................. 9
Table 3.2. Data Availability – Rhum Area Wells Loaded to Geolog .............................................. 10
Table 3.3. Rhum Sand Reservoir Zone Tops................................................................................ 10
Table 5.1. Well 3/29a – 4 Log Data Summary for Zones of Interest............................................. 13
Table 5.2. Well 3/29a – 4 Test Data.............................................................................................. 14
Table 5.3. CNC Log Environmental Correction Parameters ......................................................... 15
Table 5.4. Log Analysis Constants................................................................................................ 18
Table 5.5. 3/29a – 4 DST1B Water Analysis................................................................................. 20
Table 5.6. 3/29a – 4 RW from Core Brine Extracts....................................................................... 21
Table 6.1. Comparison of Core vs Log Defined Sands................................................................. 25
Table 8.1. Rhum Formation Pressure Data................................................................................... 31
Table 9.1. Saturation-Height Functions Derived from Air-brine Capillary Pressure Measurements.
........................................................................................................................................................ 35
Table 10.1. 3/29-2 Reservoir Properties ....................................................................................... 37
Table 10.2. 3/29a-4 Reservoir Properties ..................................................................................... 37

List of Enclosures

      1. 3/29a –4 Detailed CPI, 1:500
      2. 3/29a –4 Simplified CPI, 1:500
      3. 3/29 – 2 CPI, 1:500




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                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005


APPENDICES

A1. Geolog Database Structure
A2. Core Data Listings
A3. SCAL Results




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                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




1.       EXECUTIVE SUMMARY

     The Rhum Field contains high pressure and high temperature (HPHT) dry gas in late Jurassic
     thinly-bedded turbidite sands. The sands are informally named as the Rhum Sand and belong
     to the J74 to J62 sequences. The field has only three well control points: 3/29 – 1, 3/29 – 2 and
     3/29a – 4.

     3/29 – 1 encountered sands below Cretaceous mudstones that are of inferred late Jurassic age
     but cannot be dated conclusively. The well took a gas kick, was not logged across the
     reservoir, and was terminated 3 metres into the sand. In 3/29 – 2 the entire 148-metre gross
     thickness Rhum Sand reservoir was gas-bearing. The well was not tested because suitable
     HPHT test equipment was not developed at the time of drilling (1977). Only two valid Repeat
     Formation Tester (RFT) pressure points were obtained. A single 14-metre core was cut in a
     thinly-interbedded sand interval. A basic gamma ray-density-resistivity-sonic log suite was
     obtained. Core indicated that the reservoir was a thinly-bedded turbidite sequence. 3/29a – 4,
     drilled in 2000, encountered 191 metres of gross Rhum reservoir, drilled through a gas-water
     contact, and was successfully tested. 93 metres of core were cut, out of 191 metres of reservoir
     (nearly half the entire reservoir sequence). In order to resolve and quantify reservoir quality in
     the thinly-bedded sequence, a comprehensive suite of log and pressure data was acquired.

     This report details log analysis incorporating special core analysis (SCAL) data from 3/29a – 4
     and includes a re-analysis of 3/29 – 2.

     The selected logging program was largely successful in 3/29a – 4 and did improve thin sand
     definition. It is important to have a range of logging tools to address separate but related
     aspects of reservoir quality. Thus the best tool for determining gas saturation and sand volume
     overall was the Magnetic Resonance Imaging Log (MRIL); while individual thin bed quality was
     best measured by high-resolution density logs, and the 3D Explorer Induction Log (3DEX)
     tensor resistivity tool.

     It was difficult to get an accurate measure of water saturation from log and core data. Core
     saturation data in 3/29a – 4 indicated very low water saturations in the gas leg. Although the
     direct core saturation data agreed with the MRIL saturations, other indicators (log SW and
     capillary pressure data) suggest higher water saturations in the gas leg. Core saturation data
     should be reviewed. Special core analysis of 3/29a – 4 core provided refined Archie parameter
     values, porosity and permeability data corrected for reservoir pressure and overburden,
     confirmation of formation water resistivity and saturation-height data. Very thin, cm-scale, sand
     beds were seen in core that are not detectable on logs but are likely to contribute to production.

     Reliable pressure data were obtained that define gas and water gradients and a free water level
     (FWL) at 4745mTVDSS. The FWL indicated by formation pressure and core data is consistent
     with the log data.

     Given the HPHT nature of the gas volume, even low permeability sands are likely to contribute
     to production. Net sand is therefore defined as equivalent to gross sand. Extensive core
     indicates that the reservoir is either fine to medium-grained sand or shale and a simple sand
     flag was devised to describe net, based on matrix density and shale volume.

     Rhum Sand reservoir quality is variable, being generally moderate but ranging from poor to
     good (Summary Figures 1 and 2). The highest porosity and permeability was seen in the
     Upper Reservoir (UR) zone of 3/29 – 2, with 100% net-to-gross (NTG) averaging 16.4 porosity
     units (PU) and 255 millidarcies (mD) (zonal averages) in a 3.4m thick sand, but the same sand
     in 3/29a – 4 is only 1m thick with 50% NTG, less than 1 PU and 0.1 mD. The Upper Main
     Reservoir (UMR) zone ranges in porosity between 3.8 and 11.4 PU, permeability 0.5 to 12 mD
     and NTG 4 to 96%. Individual beds in the UMR exhibit Darcy-scale permeability. Despite the
     variability between reservoir zones, the total net reservoir thickness is similar in both wells,
     being 108m in 3/29 – 2 and 95m in 3/29a – 4.




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                                                                                                                                                                                        Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 1.1. 3/29 – 2 Rhum Well Summary – Reservoir Section

                                                                                                                                                                                                3/29 – 2 Reservoir Properties
                                                                                                                                                                                                                                  Arith.    Geom.
                                                                                                                                                                                       Gross,     Net,     NTG,     Porosity,
                                                                                                                                                                                Zone                                              Perm.,    Perm.,
                                                                                                                                                                                         m         m        %          %
                                                                                                                                                                                                                                   mD        mD
                                                                                                                                                                                UR      3.4        3.4      100       16.4         669       255



                                                    Reservoir
                     DRHO
              -0.4   G/C3    0.1




                                                                                               TVDSS
    BS               NPHI                                                                                             CORE                         PHIE
                                                                                                                                                                               UMR1    29.2       28.0      96        11.2         250        9




                                                                                      METRES



                                                                                                       METRES
                                                                              Depth
                                                                Zone
6    IN    16 0.45    V/V   -0.15                                                                               10     IN    0                1    V/V    0
    CALI             RHOB               ILD                                                                           CPOR           NET           BVW             K
6   IN     16 1.95   G/C3   2.95 0.2   OHMM   200                                                               0.3    V/V   0 10   METRES   0 1   V/V    0 0.1    MD 10000


0
    GR
    GAPI 200 140
                      DT
                     US/F     40 0.2
                                       SFLU
                                       OHMM   200                                                               0.3
                                                                                                                      PHIE
                                                                                                                      V/V    0 1
                                                                                                                                     SWE
                                                                                                                                     V/V     0 0
                                                                                                                                                   VSH
                                                                                                                                                   V/V    1 0.1
                                                                                                                                                                  CKHA
                                                                                                                                                                  MD   10000
                                                                                                                                                                               UMR2    19.4       12.7      65        11.4             85    11
                                                                              4510
                                                                              4515
                                                                                               4480
                                                                                                                                                                               UMR3    20.9       19.1      91        7.4              14     1
                                                                                               4485
                                                                              4520
                                                    KCF
                                                        31                    4525
                                                                                               4490
                                                                                               4495
                                                                                                                                                                                LMR    50.5       44.4      88        2.8              4     0.1
                                                                              4530
                                                                                               4500
                                                                              4535
                                                                                               4505                                                                                                      Averages on total sand flag
                                                                       4507 4540
                                                      UR               4511 4545               4510
                                                                                               4515
                                                                              4550
                                                     IRS                      4555
                                                                                               4520
                                                        20
                                                                                               4525
                                                                              4560
                                                                       4532 4565
                                                                                               4530
                                                                                               4535
                                                                                                                                                                               Top Main Rhum
                                                                              4570
                                                                              4575             4540                                                                            Reservoir
                                                    UMR1                      4580             4545
                                                        29
                                                                              4585             4550
                                                                              4590             4555
                                                                       4561 4595               4560
                                                                                               4565
                                                                                                                                                                               Reservoir not flow tested
                                                                              4600
                                                    UMR2                      4605             4570
                                                        19
                                                                              4610             4575
                                                                       4580 4615               4580
                                                                              4620             4585
                                                    UMR3                      4625             4590
                                                        21
                                                                              4630             4595
                                                                              4635             4600
                                                                       4601
                                                                              4640             4605
                                                                              4645             4610
                                                                              4650             4615                                                                            FWL below base
                                                                              4655             4620
                                                    LMR                       4660             4625
                                                                                                                                                                               reservoir at 4745
                                                        50                    4665
                                                                              4670
                                                                                               4630
                                                                                                                                                                               mTVDSS
                                                                                               4635
                                                                              4675
                                                                                               4640
                                                                              4680
                                                                                               4645
                                                                              4685




                                                                                                                                                                  Page 5
                                                                                                                                                                                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 1.2. 3/29a – 4 Rhum Well Summary – Reservoir Section

                                                                                                                                                                                                                     3/29a – 4 Reservoir Properties
                                                                                                                                                                                                                                                          Arith.   Geom.
                                                                                                                                                                                                                  Gross,   Net,     NTG,    Porosity,




                                                   Reservoir
                    DRHO                                                                                               CORE                                                                              Zone                                             Perm.,   Perm.,
             -0.4   G/C3     0.1                                                                               10       IN        0                                                                                 m       m        %         %
                                                                                                                                                                                                                                                           mD       mD




                                                                                              TVDSS
    BS              NPHI                                                                                             COREPHIH1                          PHIE




                                                                                     METRES



                                                                                                      METRES
                                                                             Depth
                                                               Zone
6    IN   16 0.45    V/V   -0.15                                                                               30        %        0                1    V/V    0
    CAL             RHOB              M1RX                                                                           COREICPHI1           NET           BVW            K
6   IN
    GR
          16 1.95   G/C3
                     DT
                           2.95 0.2   OHMM
                                       RV
                                             200                                                               30        %
                                                                                                                        PHIE
                                                                                                                                  0 10   METRES
                                                                                                                                          SWE
                                                                                                                                                  0 1   V/V
                                                                                                                                                        VSH
                                                                                                                                                               0 0.1   MD
                                                                                                                                                                        K
                                                                                                                                                                            10000
                                                                                                                                                                                                         UR        1.0     0.5       50        0.5         0.2      0.1
0   GAPI 200 140    US/F     40 0.2   OHMM   200                                                               0.3      V/V       0 1     V/V     0 0   V/V    1 0.1   MD   10000



                                                                             4640
                                                                                              4610                                                                                                      UMR1U     17.9     0.7        4        3.8          3       0.4
                                                                                              4615
                                                                             4645
                                                   KCF
                                                       33
                                                                             4650
                                                                                              4620
                                                                                              4625
                                                                                                                                                                                                        UMR1L     26.8     17.9      67        9.2          70      12
                                                                             4655
                                                                                              4630

                                                                                                                                                                                                        UMR2      22.3     5.0       22        6.9          1       0.5
                                                                             4660
                                                                                              4635
                                                              4665
                                                      UR 4639                                 4640
                                                                             4670

                                                                                                                                                                                                        UMR3      12.9     10.4      81        6.8          18       1
                                                                                              4645
                                                                             4675
                                                    IRS                      4680
                                                                                              4650
                                                       25
                                                                             4685
                                                                                              4655
                                                                                              4660
                                                                                                                                                                                      Top Main           LMR      61.0     45.1      74        6.4          4       0.2
                                                                             4690
                                                                      4665
                                                                             4695
                                                                                              4665
                                                                                                                                                                                      Rhum
                                                                                                                                                                                                         LR       47.6     15.4      32        7.1         1.3      0.2
                                                                                              4670
                                                                             4700
                                                                             4705
                                                                                              4675
                                                                                              4680
                                                                                                                                                                                      Reservoir
                                                                             4710
                                                   UMR1                                       4685                                                                                                                                Averages on total sand flag
                                                                             4715
                                                       45
                                                                             4720
                                                                                              4690
                                                                                              4695
                                                                                                                                                                                                 DST 2
                                                                                                                                                                                             •   45 mmscfg/d
                                                                             4725
                                                                                              4700
                                                                             4730
                                                                                              4705

                                                                                                                                                                                             •   270 bbl cond/d
                                                                             4735
                                                                      4710                    4710
                                                                             4740
                                                                                              4715

                                                                                                                                                                                             •
                                                                             4745
                                                   UMR2
                                                       22                    4750
                                                                                              4720
                                                                                              4725
                                                                                                                                                                                                 CGR 6 bbl/mmscf
                                                                                                                                                                                             •
                                                                             4755
                                                                      4732 4760
                                                                                              4730
                                                                                              4735
                                                                                                                                                                                                 6.5% CO2, 10 ppm
                                                   UMR3                      4765
                                                       13
                                                                      4745
                                                                             4770
                                                                                              4740
                                                                                              4745                                                                                    FWL        H2S
                                                                             4775
                                                                                              4750
                                                                             4780
                                                                                              4755
                                                                             4785
                                                                                              4760
                                                                             4790
                                                                                              4765
                                                                             4795
                                                                                              4770
                                                                             4800
                                                   LMR
                                                       61                    4805
                                                                                              4775
                                                                                              4780
                                                                                                                                                                                               DST 1B upper
                                                                             4810
                                                                             4815
                                                                             4820
                                                                                              4785
                                                                                              4790
                                                                                                                                                                                             • 3096 bbl water/d
                                                                                              4795
                                                                             4825
                                                                                              4800
                                                                             4830
                                                                      4806 4835               4805
                                                                                              4810
                                                                             4840
                                                                                              4815
                                                                             4845
                                                                                              4820
                                                                             4850
                                                                                              4825
                                                                             4855
                                                      LR                                      4830
                                                       48                    4860
                                                                             4865
                                                                                              4835
                                                                                              4840
                                                                                                                                                                                               DST 1B lower
                                                                                                                                                                                             • No flow
                                                                             4870
                                                                                              4845
                                                                             4875
                                                                                              4850
                                                                             4880




                                                                                                                                                                                    Page 6
                                               Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




2.       INTRODUCTION AND SCOPE

     The Rhum Field contains high pressure and high temperature (HPHT) dry gas (88.8 mol%
     methane) in late Jurassic thinly-bedded turbidite sands. The sands are informally named as the
     Rhum Sand and belong to the J74 to J62 sequences. The field has only three well control
     points: 3/29 – 1, 3/29 – 2 and 3/29a – 4 (Figure 2.1).

     3/29 – 1 encountered sands below Cretaceous mudstones that are of inferred late Jurassic age
     but cannot be dated conclusively. The well took a gas kick, was not logged across the
     reservoir, and was terminated 3 metres into the sand. 3/29 – 2 (off-crest) and 3/29a – 4 (flank)
     encountered complete Rhum Sand sequences.

     In 3/29 – 2 the entire 148-metre gross thickness Rhum Sand reservoir was gas-bearing. The
     well was not tested because suitable HPHT test equipment was not developed at the time of
     drilling (1977). Only two valid repeat formation tester (RFT) pressure points were obtained. A
     single 14-metre core was cut in a thinly-interbedded sand interval. A basic gamma ray-density-
     resistivity-sonic log suite was obtained.

     3/29a – 4, drilled in 2000, encountered 191 metres of gross Rhum reservoir, drilled through a
     gas-water contact, and was successfully tested. 93 metres of core were cut, out of 191 metres
     of reservoir (nearly half the entire reservoir sequence). A comprehensive suite of logs and
     pressure data were acquired. An operations preliminary log interpretation was performed by
     Production Geoscience Limited (PGL) (Whitehead, 2001). Recognising from 3/29 – 2 core that
     the reservoir was thinly bedded, high resolution density (ZDL) and resistivity (High Definition
     Induction Log – HDIL, and 3D Explorer induction log tensor resistivity tool - 3DEX) logs were
     acquired by Baker Atlas GeoScience (BA), together with Magnetic Resonance Imaging Log
     (MRIL) and sonic (Cross Multipole Array Acoustilog - XMAC Elite) data. BA performed in-house
     processing and interpretation of the data (Page, 2001), specifically:

     •   Depth shifting, bad data repair and log compositing;
     •   Extraction of horizontal (RH) and vertical (RV) components of resistivity from 3DEX data via
         inversion;
     •   Enhancement of vertical resolution of density, neutron, and HDIL logs;
     •   Determination of apparent fluid volumes from MRIL.

     The BA report should be consulted for log processing details.

2.1.     Workscope

     This report details the updated log analysis incorporating special core analysis (SCAL) data
     from 3/29a – 4 and also includes a re-analysis of 3/29 – 2. The scope of work comprised:

     •   Quality check and update Geolog database, check environmental corrections and load
         necessary additional data including PGL curves and SCAL-corrected core data;
     •   Review of PGL petrophysical analysis of 3/29a – 4;
     •   Update analysis of 3/29a – 4 with previously uninterpreted high resolution log data and
         new SCAL data. This analysis will improve thin sand bed resolution and water saturation
         determination;
     •   Correct core porosity data for overburden and core permeability data for reservoir
         conditions. Use core data to calibrate log-derived porosity and permeability;
     •   Comparison of porosity and water saturation analysis derived from different tools (nuclear,
         electric and magnetic resonance imaging logs) and matched to core data;
     •   Evaluate whether higher resolution density and resistivity tools have added value to well
         results and aided net definition;
     •   Re-evaluate 3/29 – 2 logs using Archie parameters derived from 3/29a – 4 SCAL;
     •   Determine best net sand flag;
     •   Generate permeability logs;
     •   Confirm free water level;


                                               Page 7
                                                                                                 Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



    •            Generate reservoir zone averages;
    •            Export data for RMS 3D geological model build.

2.2.           Depth Conventions

    All depths and thicknesses are quoted in metres (m) and unless otherwise specified are logged
    depth below reference datum. True logged vertical depth below reference datum and true
    logged vertical depth subsea are indicated as TVD and TVDSS respectively. Drilled depths are
    indicated as mDD, mTVDDD or mTVDSSDD.


Figure 2.1. Rhum Field Location Map



                     B               C
         23a             19b
                         24c                    25c  Nuggets
                                                                       21
                                                                                                                                     HWC
                     23b 24b                D
                                          24a                    25b
                                                                       10a            11a


                                                                                      11c

    28a                  29a               29d
                                             30a                       26

         28b                                          30b

                                          29b                                         11b
               28c
                               29c
                                          Rhum
                                                                                                                            3/29a-4
a   3a     3b            4a         4c          5b          5a         10/1 1b        2a    2c
Bressay                   4b
                         4d                                                  25/1a
                                            Frigg
                                                                                                                                3/29-2
    8b                   9c                     10a                    6                                                    3/29-1
                                                                 10c
                 8a      9b          9a

                                                                       4b             5b
                                                10b

                               9d
                                     Bruce                                       4c
                                                                  6
                                                                                 4a
    13e        13d       14a                    15a                                                                                              1km




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                                                             Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




3.        FIELD AND WELL DATABASE

     Tables 3.1 to 3.3 list basic Rhum Field information and data availability. Geolog database
     listings are provided in Appendix 1, identifying the names of best log and core datasets. Note
     that complete sequence, group, formation and reservoir zone tops from surface to TD are
     included in the Geolog database as ZONE.SEQUENCE, ZONE.GROUP, ZONE.FORMATION
     and ZONE.ZONE.


Table 3.1. Rhum Field Data
      PROPERTY                                     VALUE            UNITS      NOTES

      LOCATION
      Field / Block                                 3/29a                      ca.45km N of Bruce, 35km NW of Frigg
      Latitude                                    60 08' 13"          N        3/29a-4 location
      Longitude                                   01 42' 50"          E        3/29a-4 location
      Water Depth                                   108.5           metres     MSL - no significant variation across field

      TRAP
      Type                                     4 way dip closure               Reservoir interval drapes Triassic fault block
      Area                                        3.50E+07           m2        Dimensions approx 10km (N-S) by 5km (E-W)
      Gross Rock Volume                           1.99E+09           m3        Base Case (range 1.87-2.28 E+09 m3)
      Depth to Crest                                 4400          mTVDSS
      Lowest closing contour                         4880          mTVDSS
      GWC                                           ?4731          mTVDSS      Probable transition zone above FWL
      FWL                                            4745          mTVDSS
      Gas Column                                      345          mTVDSS
      Oil Column                                       0           mTVDSS
      Original Pressure @ datum                     12418            psia @4745m (welltest Pi 12350psia @4619m)
      Current Pressure @ datum                      12418            psia Some evidence for higher pressures in aquifer
      Pressure Gradient                              0.17           psi/ftReservoir gradient (PVT gradient closer to 0.14 psi/ft)
                                                                          @ 4745 mTVDss (6 Deg /100m apparent res. temp grad.
      Original Temp                                 149.6           deg C
                                                                          (From Horner plots of wireline logs))
      Datum Depth                                    4745          mTVDSS FWL

      RESERVOIR
      Formation                                   Rhum Sand                    Analogous to Brae, but a separate sand system
      Age                                        Late Jurassic                 Intra-Kimmeridge
      Type                                     Turbidite Sands                 Thin-bedded sand units within basin-floor fan
      Gross Thickness                                 200           metres     Approx - thickens on western flank
      Net:Gross                                      0.25           fraction   Average - varies laterally and by reservoir unit
      Porosity average (range)                 0.09 (0.06-0.12)        v/v     Extent of qtz. cement controls resr. quality
      Permeability average (range)              45 (0.01 - 530)       mD       From core in 3/29a-4
      Hydrocarbon saturation average (range)          86               %       SCAL measurements - log satns. unreliable in thin sands

      WELL TEST PERFORMANCE
      AOFP                                            297          mmscf/d 3/29a-4 performance
      Test Kh                                        1450           mDm    3/29a-4, DST2
      Test Rate                                       45           mmscf/d 3/29a-4, DST2, drawdown 575psi, 1/2" choke

      PETROLEUM
      Gas Gravity                                   0.65              air=1
      Condensate Density                            0.788            g/cm3
      Condensate Viscosity                           0.25               cp    at Pi
      Water Viscosity                                0.25               cp    at 146deg C
      Dew point                                     5640               psia   at 148deg C
      CGR                                             6            stb/mmscf
      Gas Expansion Factor                           384             scf/rcf
      Water Formation Volume Factor                  1.03             rb/stb
      Condensate Compressibility                                              not yet determined
      Water Compressibility                       5.76E-07           1 / psia
      Formation Compressibility                   7.00E-06           1 / psia From SCAL on core samples from well 3/29 a4

      FORMATION WATER
      Salinity                                      15800            mg/l      chlorides -unusually low salinity for UJ marine resr.
      Resistivity                                   0.075           ohmm       @140deg C

      FIELD CHARACTERISTICS
      GIIP                                          1168             Bcf       Mean case, range 703-1720 Bcf (p90-p10)
      STOIIP (condensate)                             7             mmbbl      Mean case, range 4.2 -10.3 mmbbl (p90-p10)
      Recovery Factor (gas)                          70              %         Base case, range of scenarios considered
      Recovery Factor (condensate)                   60              %
      Drive Mechanism                           Gas expansion                  Aquifer movement less significant than gas blowdown
      Recoverable Gas                                803             Bcf       Probabilistic (Range 458-803-1072 Bcf, P90-P50-P10)
      Recoverable Condensate                        4.23            mmbbl      Probabilistic (Range 2.75-4.23-4.34 Bcf, P90-P50-P10)


                                                             Page 9
                                           Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Table 3.2. Data Availability – Rhum Area Wells Loaded to Geolog

     Well      Date       Log Data over         Mud        RTE,           Late Jurassic
                            Reservoir           Type       mamsl        Reservoir Presence

   3/24b – 2   1986             N/a             OBM           22           No late Jurassic
                                                                         reservoir – Shetland
                                                                            Platform well
   3/25a – 3   1977      GR, RHOB, NPHI,        OBM           24         Gas shows in v. thin
                             ILD, DT                                            sands
   3/25a – 4   1985      GR, RHOB, NPHI,        OBM          26.5           V. thin sands
                             ILD, DT
   3/29 – 1    1973           None              WBM           34        Probably drilled 3m
                                                                           into reservoir
   3/29 – 2    1977       GR, RHOB, NPHI,       WBM          25.2       Rhum discovery well
                        ILD-SFLU, LLD-LLS-
                              MSFL, DT
   3/29a – 4   2000        MWD plus high        OBM          23.5          Suspended gas
                          resolution wireline                                 producer
                         ZDL density, 3DEX
                         and HDIL resistivity
                          tools, XMAC Elite
                         sonic, CBIL imager,
                                 MRIL
   3/29b –     1992       GR, RHOB, NPHI,       WBM          26.2            Thin sands
    3&S1                 LLD-LLS-MSFL, DT


Table 3.3. Rhum Sand Reservoir Zone Tops

                                 3/29 – 2                          3/29a – 4
       Zone Name      Zone Top,        Zone Top,        Zone Top,         Zone Top,
                         mMD            mTVDSS             mMD            mTVDSS
          KCF            4508             4476            4633.5             4606
          UR             4540             4507            4666.5             4639
          IRS            4544             4511            4667.5             4640
            UMR1U          -                -             4692.5             4665
   UMR1
            UMR1L        4565             4532             4710              4683
         UMR2            4595             4561            4737.5             4710
         UMR3            4615             4580             4760              4732
         LMR            4636.5            4601             4773              4745
           LR              -                -             4834.5             4806
        Heather          4688             4651             4883              4855
       Devonian          4852             4810               -                 -
       Basement          5147             5105               -                 -
           TD            5165             5123             5060              5031
 KCF – Kimmeridge Clay Formation, UR – Upper Reservoir, IRS – Inter Reservoir Shale, UMR –
         Upper Main Reservoir, LMR – Lower Main Reservoir, LR – Lower Reservoir.




                                          Page 10
                                               Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




4.               FIELD TEMPERATURE AND PRESSURE

     As stated in the Introduction, Rhum is considered to be an HPHT field. Wells with undisturbed
     bottomhole temperature above 150oC (302oF) are classed as high temperature. Those with
     wellhead pressure greater than 10,000 psi or a maximum anticipated downhole pore pressure
     exceeding an 0.8 psi/ft hydrostatic gradient are considered high pressure (Baird et al., 1998).

     The highest reliable corrected bottom hole temperature (BHT) registered while logging in 3/29a
     – 4 was 155oC at 4,919.4 m (Run 4A in 8.5-inch hole). This would yield an extrapolated BHT at
     total depth (TD - 5,060 m) of 163.3oC (Watts, 2001). A temperature gradient for the Jurassic
     and Devonian interval of 5.94oC/100m was computed from BHT data from Runs 3 and 4 (Watts,
     2001). For log analysis purposes, the near-bore formation temperature at time of logging is
     more important. TD logging Run 5 registered 141.1oC at 4,927mTVDSS after 22.6 hours no
     circulation and this value was combined with the temperature gradient data to determine near-
     bore reservoir temperature distribution at time of logging (Figure 4.1).

     The maximum measured shut in pressure recorded at the wellhead in 3/29a – 4 was 10,190 psi.
     The maximum downhole pressure in the gas leg was 12,418 psi at 4,745 mTVDSS in 3/29a – 4.
     The maximum downhole pressure in the water leg was 13,493 psi at 4,838 mTVDSS in 3/29 – 2
     (Figure 4.2). More information on formation pressure is given in Section 8.

Figure 4.1. 3/29a – 4: Temperature Gradient used in Log Analysis



                                Temperature Gradient, 3/29a-4

                     -4550
                          100   110   120       130         140        150        160        170
                     -4600                            Top KCF

                     -4650

                     -4700
                                                         Jurassic temperature gradient
                                                         5.94 degC/100m
                     -4750
      Depth, TVDSS




                     -4800

                     -4850               Top UMR1
                                           Sand
                     -4900
                                                                      Run 5 log temp –
                                                                      141.1degC @ 4927m
                     -4950

                     -5000

                                                                          TD @ 5031m
                     -5050

                     -5100
                                                Temp., degC
                                              Page 11
                                                            Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 4.2. Rhum Field Formation Pressures


                                               Rhum Reservoir Pressure psi
                       12000   12200   12400     12600   12800    13000      13200   13400   13600
                    4300




                    4400




                    4500

                                                                                                       crest
      depth tvdss




                                                                                                       3/29-1
                    4600
                                                                                                       3/29-2
                                                                                                       3/29a-4

                    4700




                    4800




                    4900




                                                           Page 12
                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




5.       WELL – BY – WELL EVALUATION

     This section describes the updated petrophysical evaluations conducted on 3/29a – 4 and 3/29
     – 2. 3/29a – 4 was evaluated first, then 3/29 – 2 was reanalyzed using the SCAL data from
     3/29a – 4.

5.1.     3/29a – 4 Review

5.1.1. 3/29a – 4 Data
     3/29a – 4 was drilled with a synthetic oil-based mud (SOBM). Hole deviation is low (maximum
     5.7 degrees at 4947m). The well reached TD at 5060m in the Heather Formation.

     Log and test data are listed below (Tables 5.1 and 5.2). Log curve mnemonics are listed in
     Appendix 1. Four intervals were perforated and tested. Note that only the UMR zone flowed
     gas. Deeper intervals were perforated and tested because the initial evaluation conducted by
     PGL indicated deeper hydrocarbons. The cause of this was use of an incorrect estimated
     formation water resistivity (RW) value. The water recovered on test allowed refinement of the
     RW value used in this updated analysis.

     Logging was conducted by BA and was problematic, with multiple runs being made.
     Intermediate logs suffered from tool sticking. TD logs were of better quality although there were
     still zones of sticking and TD logs only reached a maximum depth of 4980m, not reaching the
     well TD of 5060m. Log data were loaded to Geolog (Appendix 1). 93m of core were cut and
     cored intervals are listed in Appendix 2. Conventional and SCAL core analyses were
     conducted by Corex and Integrated Core Consultancy Services Limited (ICCS). ICCS data
     were generally considered to be of better quality and were used for log calibration purposes.
     SCAL data are reviewed in Appendix 3. Key input curves and data are plotted on the CPI,
     Enclosure 1.

Table 5.1. Well 3/29a – 4 Log Data Summary for Zones of Interest

     Run No.                   Logs Run                      Interval         Date Run       Hole
                                                          Logged, mMD                        Size,
                                                                                            inches
     LWD 12-      GR-MPR-MAP-DIR (+CCN-ORD on               4525-4961          11/10-         8.5
       15                   run 14)                                           29/11/00
      WL3A                FMT-GR-CHT                       4664-4693.6        17/10/00        8.5
      WL4A         GR-HDIL-3DEX-ORIT-XMACII-                4963-4514         30/11/00        8.5
                             TTRM
       WL4A            ZDL-CN-DSL-TTRM                      4910-4514          1/12/00        8.5
       WL4A               FMT-GR-CHT                       4717-4880.5         1/12/00        8.5
       WL4A              RCI-GR-TTRM                      4717.5-4834.6        1/12/00        8.5
       WL4B              RCI-GR-TTRM                      4717.5-4783.5        2/12/00        8.5
       WL4C              RCI-GR-TTRM                        4790-4859          2/12/00        8.5
       WL4B               FMT-GR-CHT                      4784.5-4861.8        3/12/00        8.5
       WL4C               FMT-GR-CHT                       4733.9-4882         3/12/00        8.5
       WL4A              MRIL-GR-TTRM                       Failed – no        4/12/00        8.5
                                                               data
       WL4B                MRIL-GR-TTRM                     4900-4675         4/12/00         8.5
       WL4D                RCI-GR-TTRM                     4788-4851.5         5/12/00        8.5
       WL4E                RCI-GR-TTRM                         4835            5/12/00        8.5
       WL4A             HDIP-CBIL-GR-TTRM                   4910-4514         6/12/00         8.5
       WL5A        GR-HDIL-XMAC-ORIT-TTRM*                  4980-4650         11/12/00        8.5
       WL5A             ZDL-CN-DSL-TTRM*                    4915-4776         11/12/00        8.5
       WL5A                  DMAG-GR*                        4510-130         12/12/00        8.5
     *TD logs marked with an asterisk.



                                               Page 13
                                             Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Table 5.2. Well 3/29a – 4 Test Data

    Test         Top of          Bottom of        Shot                     Result
    No.        Perforated        Perforated      Spacing,
             Interval, mMD     Interval, mMD       SPF
   DST1A          4844              4883            6               LR zone – no flow
   DST1B          4777             4829.5           6         LMR & LR zones – 3096 BWPD,
                  4844              4833            6              15800 mg/l salinity
   DST2A          4692              4735            6         UMR zone – 45 mmscfgpd, CGR
                                                                     6.4 stb/mmscf


   Log data were loaded to Geolog by previous users during well operations. Existing naming
   conventions were confusing and have been updated (see Appendix 1). Best datasets are
   depth-referenced to the Run 5A down log (BA_FINAL_LORES_GR_REF_1 or
   BEST.GR_REF_1 reference gamma ray log). GR_REF should not be used for analysis since it
   is a mix of centralized and decentralized sensor data and is for depth reference purposes only.
   The best set of logs are the ones in sets prefixed BA_FINAL, and key logs have been copied
   from BA_FINAL sets to a single BEST set.

   Operations petrophysical analysis was performed by PGL (Whitehead, 2001) with BA
   Geoscience conducting additional studies (curve processing and corrections, MRIL data
   analysis and thin bed resistivity modelling). BA made necessary environmental corrections but
   PGL additionally corrected the neutron CNC log for pressure, mud weight and borehole
   temperature (curve named CCNC).

   Both BA and PGL spliced logs to obtain coverage over bad data areas. The BA composited
   logs were used in the PGL analysis. The first step in this review was to understand the origin
   and significance of existing Geolog data and to update the database with formation tops from
   OpenWorks and with perforations/test data.

   A petrophysical database was constructed within Geolog. Database specifics, including
   environmental corrections and core shifts applied are provided in Appendix 1 and 2. SCAL
   results are provided in Appendix 3.

5.1.2. Review of PGL Analysis
   A layout was built to show PGL results (SK_329A_4.layout). This was used to check we had
   the correct PGL data set. All the curve data provided by PGL are retained in the Geolog dataset
   called PGL (input curves and calculated curves).

   As a background check on the PGL method and software the PGL analysis was partially
   duplicated. Input curves matching those used by PGL are in the BEST_PGL dataset.
   Calculated curves are in the CALC_PGL data set.

5.1.2.1.    Environmental Corrections
   Note that the only environmental correction made by PGL was to the CNC log. PGL believed
   that BA had made all other required corrections but this was not the case. Corrections are
   required for mud weight to the GR, density and PE logs. Resistivity logs were borehole-
   corrected in real-time. The CNC log is borehole-corrected compensated (caliper and salinity)
   neutron logs. The CNCC log is additionally corrected for pressure, mud weight and borehole
   temperature. The PGL environmental correction (PGL.CNCC) was duplicated in Geolog
   (BEST_PGL.CNCC) as a check on the PGL method. Table 5.3 lists the input parameters
   derived from the Run 5A log header. There was good agreement between the two curves. The
   same corrections were applied to the BEST.NPHI and BEST.CNHR curves.




                                            Page 14
                                             Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Table 5.3. CNC Log Environmental Correction Parameters

                Parameter                          Units                      Value
  CNC Tool Type                                                              2446XA
  Standoff                                       Inches                    Decentralized
                                                    O
  Top Log Interval Temperature (TLT)                 F                         60.8
  Top Log Interval Depth (TLI)                  Metres MD                      128
                                                    O
  Bottom Log Interval Temperature (BLT)              F                         286
  Bottom Log Interval Depth (BLI)               Metres MD                      4899
  Mud Weight (DFD)                               Lb/gal                       15.94
  Bit Size (BS)                                  Inches                         8.5
  Mud type                                                                    SOBM
  Mud oil/water ratio                                                         82/18
  Whole mud chlorides                              Mg/l                      23,750
  Mud salinity                                     Mg/l                      38,229
  Mud contains barite?                                                     Yes, 30.65%



5.1.2.2.  Shale Volume (VSH)
  Computed by reservoir interval using input parameters listed in PGL report (Whitehead, 2001,
  Appendix 2). VSH computed using gamma ray from resistivity logs (VSHGR), neutron (VSHN)
  and neutron/density (VSHDN). Good agreement with PGL curves. PGL comparison is in
  CALC_PGL.

5.1.2.3.   Effective Porosity (PHIE)
  Effective porosity computed using PGL constants and Bateman-Konen density-neutron method.
  Resulting curve (CALC.PGL_PHIE) is very similar.

5.1.2.4.   Water Saturation (SW)
  The PGL petrophysical analysis was run using the 3DEX vertical resistivity component, RV, for
  true formation resistivity (RT) as input to the Indonesia Equation (RV gives a better measure of
  thin bed resistivity than horizontal resistivity, RH) over the UMR1. Below the UMR1, the HDIL
  120-inch depth of investigation (M2RX) curve was used for RT. The curve is PGL.RTCOMP.
  However, the RV curve cannot be used to compute saturations using the Indonesia Equation
  because the Indonesia Equation is designed to use horizontal resistivity measured in parallel
  along beds rather than in series across beds. The result would tend to underestimate SW. The
  3DEX data must be interpreted using BA software with informed user input. Since this method
  was not valid it was not repeated.

5.1.3. MRIL Processing
  MRIL analysis method is described by Page (2001). MRIL data are loaded in Geolog in the set
  BA_FINAL.MRIL. MRIL curves are displayed on the enclosed CPI (track 16, Enclosure 1).
  Note that the MRIL curves displayed have been summed to indicate the different fluid fractions:

   •   PHS, total porosity = MCBW + MPHI

       PHS is the sum of clay-bound water (MCBW) plus mobile fluids or effective porosity
       (MPHI).

   •   MPHI, effective porosity = MBVI + MFFI

           MPHI is the sum of capillary-bound water (MBVI) plus free fluids (MFFI).

   •   MFFI may be mobile water (MWATER), oil (MOIL) and gas (MGAS).

   •   MWATER = MBVI + MRIL_WATER


                                             Page 15
                                              Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




   •   MOIL = MWATER + MRIL_OIL

   •   MGAS = MOIL + MRIL_GAS

   •   PHS also equals MGAS + MCBW (in this case the sum MGAS equals MPHI)

  In this case MOIL represents the invaded phase of the oil-base mud and not oil in the formation.
  Summed curves are located in the set PGL. Note that PGL.MRIL_SW (track 14, Enclosure 1)
  measures irreducible SW, and therefore only indicates true SW above the free water level. The
  MRIL tool has a 2-foot vertical resolution and the resultant curves are very smooth compared to
  electric log curves.

5.1.4. New Petrophysical Analysis
  Best input curves are located in the BEST Geolog dataset. Computer-processed log
  interpretation (CPI) plots are enclosed (Enclosure 1 – detailed analysis, Enclosure 2 –
  simplified display).

5.1.4.1.    Environmental Corrections
  The gamma ray (GRR) log is corrected for hole size and mud weight since there is no evidence
  of prior corrections having been made. The corrected curve is BEST.GRR.

  High resolution density (BEST.DNHR), neutron (BEST.CNHR) and HDIL induction log
  (BEST.M1R) data were used for the updated analysis. DNHR and PE curves were corrected
  for borehole size. DNHR was renamed as RHOB (bulk density). CNHR log corrected as
  described above, and renamed as NPHI. HDIL curves were corrected by BA for borehole
  conditions. Zones where HDIL component curves do not overlie each other are likely due to
  stick and pull effects, which were corrected as far as possible, and not due to invasion.

5.1.4.2.   Analysis
  The petrophysical analysis was run from top Kimmeridge Clay Formation to TD, which included
  the Rhum reservoir sands and the underlying Devonian interval. Input constants are listed in
  Table 5.4. Where the same value is indicated in the table this is because there was insufficient
  difference or data to vary the constants between intervals. Note that the same input parameters
  were applied to the Devonian interval as for the Rhum Sand, and the Devonian analysis should
  be considered quick-look only.

5.1.4.3.   VSH
  The best VSH method was considered to be a normalized gamma ray because density and
  neutron logs could be affected by gas in the shales that is not easily detected or corrected for
  using Geolog. The common method of taking the minimum of VSH from density, neutron and
  GR methods is flawed in gas reservoirs where the gas effect will cause underestimation of shale
  on the neutron and density logs. Different matrix and shale constants were used for the LR
  zone that exhibited a considerably higher GR than the rest of the reservoir, indicating a different
  shale type.

  VSH is computed from BEST.GRR. See GR histogram (Figure 5.1) and constants table for
  input values. Resulting curve is CALC.VSH_GR (track 17, Enclosure 1).




                                             Page 16
                                                                                                                               Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 5.1. GR Response Histograms



                      Frequency Histogram of BEST.GR_1                                                                       Frequency Histogram of BEST.GRR_COR_1
                                 Well: 3_29-2                                                                                              Well: 3_29A-4
Intervals: KCF, UR, INTER RES SHALE, UMR1, UMR2, UMR3, LMR, LR, LKCF                                                                 4633.5 - 4894.0 METRES
                                    Filter:                                                                                                    Filter:



                                                                                       1.0             0.025                                                                               1.0
   0.06
                                                                                       0.9                                                                                                 0.9

   0.05                                                                                0.8             0.020                                                                               0.8

                                                                                       0.7                                                                                                 0.7
   0.04
                                                                                       0.6             0.015                                                                               0.6

                                                                                       0.5                                                                                                 0.5
   0.03

                                                                                       0.4             0.010                                                                               0.4

   0.02
                                                                                       0.3                                                                                                 0.3

                                                                                       0.2             0.005                                                                               0.2
   0.01
                                                                                       0.1                                                                                                 0.1

   0.00                                                                                0.0             0.000                                                                               0.0
                MA                                              SH                                                  MA                                                    SH




                                                                                                               0




                                                                                                                                                                                     350
                                                                                                                      35



                                                                                                                                70



                                                                                                                                      105



                                                                                                                                              140



                                                                                                                                                     175



                                                                                                                                                           210



                                                                                                                                                                  245



                                                                                                                                                                        280



                                                                                                                                                                               315
          0




                                                                                 250
                 25



                        50



                               75



                                      100



                                             125



                                                   150



                                                          175



                                                                     200



                                                                           225




          Statistics:                                                                                          Statistics:

          Possible values                  242                                                                 Possible values                    6837
          Missing values                     0                                                                 Missing values                        0
          Minimum value
          Maximum value
                                      14.59800
                                     189.63300           GR_MA 24                                              Minimum value
                                                                                                               Maximum value
                                                                                                                                              20.00517
                                                                                                                                             341.82709           GR_MA 27
          Range                      175.03500                                                                 Range                         321.82192
                                                         GR_SH 183                                                                                               GR_SH 233
          Mean                       139.62461                                                                 Mean                          156.00152
          Geometric Mean             126.97939                                                                 Geometric Mean                128.23745
          Harmonic Mean               99.56522                                                                 Harmonic Mean                  95.30654

          Variance                  1776.87826                                                                 Variance                     6405.42571
          Standard Deviation          42.15303                                                                 Standard Deviation             80.03390
          Skewness                    -1.46019                                                                 Skewness                       -0.05039
          Kurtosis                     4.87954                                                                 Kurtosis                        2.07035
          Median                     145.31250                                                                 Median                        168.41034
          Mode                       171.25000                                                                 Mode                           26.25000




                                                                                             Page 17
                                              Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Table 5.4. Log Analysis Constants

                                 UR/Int.                          UMR3/LM
  Parameter     Units    KCF                 UMR1       UMR2                        LR       LKCF
                                 Res Sh                                R
 Fluid Type             Gas      Gas         Gas       Gas        Water          Water      Water
 A                      1.1      1.1         1.1       1.1        1.2/1.1        1.1        1.1
 DT_MA          US/F    55.5     55.5        55.5      55.5       55.5           55.5       55.5
                T
 DT_SH          US/F    95       90          90        85         90             90         85
                T
 DT_FL          US/F    210      210         210       210        210            210        210
                T
 GR_MA          GAPI    27       27          27        27         27             43         43
 GR_SH          GAPI    233      233         233       233        233            318        318
 M                      1.9      1.9         1.9       1.9        1.9/2.1        1.9        1.9
 MUD TYPE               SOB      SOBM        SOBM      SOBM       SOBM           SOBM       SOBM
                        M
 NPHI_COAL      V/V     N/A      N/A         N/A       N/A        N/A            N/A        N/A
 N                      1.7      1.7         1.7       1.7        1.7            1.7        1.7
 NPHI_FL        V/V     1        1           1         1          1              1          1
 NPHI_MA        V/V     -        -0.017      -0.017    -0.017     -0.017         -0.017     -0.017
                        0.017
 NPHI_SH        V/V     0.559    0.559       0.559     0.559      0.559          0.559      0.559
 PHIE_MAX       V/V     0.3      0.3         0.3       0.3        0.3            0.3        0.3
 PHIT_SH        V/V     0.052    0.052       0.052     0.052      0.052          0.052      0.052
 RES_SH         OHM     3.3      5.9         6.7       7.1        5.6            7.2        7.2
                -M
 RHO_COAL       G/CC    N/A      N/A         N/A       N/A        N/A            N/A        N/A
 RHO_DS         G/CC    2.66     2.66        2.66      2.66       2.66           2.66       2.66
 RHO_FL         G/CC    0.39     0.39        0.39      0.39       0.7            0.7        0.7
 RHO_MA         G/CC    2.647    2.647       2.647     2.647      2.647          2.647      2.647
 RHO_SH         G/CC    2.573    2.573       2.573     2.573      2.573          2.573      2.573
 RHO_W          G/CC    1        1           1         1          1              1          1
 RW             OHM     0.075    0.075       0.075     0.075      0.075          0.075      0.075
                -M
                o
 RW_TEMP         C      140      140         140       140        140            140        140
 SPI_MAX        V/V     0.1      0.1         0.1       0.1        0.1            0.1        0.1
  Underlined values are derived from core.


5.1.4.4.   PHIE
  Porosity was computed from density, density/neutron (Bateman-Konen method) and sonic
  (Wyllie method) logs. Log analysis matrix and fluid constants are included in Table 4.4.
  Computed log porosities were calibrated against core. Core porosities were corrected for
  overburden using a factor of 0.972 obtained from 3/29a – 4 SCAL analysis, using the Teeuw
  (1971) method (Appendix 3). Overburden-corrected data sets are suffixed _OBC. This is a
  very small correction reflecting the well-cemented nature of the rock.

  There are no coals in the reservoir.

  High resolution density and neutron logs (DNHR and CNHR with 1.5-inch sampling) were used
  as input, with bad data gaps infilled by lower resolution data (track 6, Enclosure 1).

  The best match to core data was obtained using the density method (track 12, Enclosure 1).
  Sonic porosity gave a good match to core in the gas leg, but was too low in the water leg. The
  water leg match could not be improved without reducing reservoir fluid sonic travel time
  (DT_FL) excessively. The density porosity calculation assumes a matrix density (RHO_MA) of
  2.647 g/cc. Core grain density values are predominantly around 2.647 g/cc except for a small
  percentage of lower grain densities in the range 2.48 g/cc to 2.58 g/cc (track 7, Enclosure 1).


                                             Page 18
                                                                                        Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



  Note that the lower the grain density the lower the computed porosity. If a value of RHO_MA is
  used that is too high, the computed porosity will also be too high. This is relevant because the
  Lower Reservoir interval 4850 – 4865 m contains four beds with computed porosity in the 15 to
  20 porosity unit (PU) range. However, MRIL porosities are lower, around 5 PU (curve
  PGL.MPHIE, track 16, Enclosure 1). A porosity of 5 PU can be matched by reducing RHO_MA
  to 2.5 g/cc. Petrographical studies (Paintal, 2002) did not identify significant amounts of lower
  density material such as clays, felspar, organic material or residual hydrocarbons in any of the
  core samples. There was not therefore a good case for lowering RHO_MA, and the anomaly
  remains. Reservoir fluid density (RHO_FL) was computed at 0.39 g/cc in the gas leg, using a
  core porosity to log density regression (Figure 5.2). This matches the measured pressure
  gradient of 0.17 psi/ft (equivalent to 0.39 g/cc). There were insufficient core data to get a
  reliable RHO_FL value in the water leg. The water leg RHO_FL value was selected based on
  an SOBM density of 0.7 g/cc. The MRIL log indicates that SOBM is the invaded phase.

  Computed porosity curves are named CALC.PHIE_DEN or CALC.PHIE (density method),
  CALC.PHIE_DN (density-neutron method) and CALC.PHIE_SON (Wyllie sonic method).

  BA (Page, 2001) computed an effective sand fraction porosity (see Geolog curve
  BA_FINAL_REPORT.PESD_1; track 13 on Enclosure 1) based on an anisotropic thin bedded,
  laminar shaly sand model utilizing the 3DEX data. This is intended to give a better volumetric
  characterization of porosity in thin sands by removing thin laminar shale effects. In thicker
  sands the result matches the density porosity. In the KCF a number of thin sands with 15 PU
  porosity are identified by this method that would be productive. However, comparing the PESD
  curve to core description indicates that the PESD curve over-estimates porosity in thick shaly
  units. Therefore the PESD curve should be treated with caution. Given the difficulty of
  identifying these sands with conventional log analysis it is recommended that the entire
  reservoir interval including the KCF is perforated if possible.


Figure 5.2. 3/29a – 4 Core Porosity vs Log Density Crossplot in the Gas Leg



                         CORE.COREICPHI1_OBC_1 vs. BEST.DNHR_1 Crossplot
                                                                                     Well: 3_29A-4
                                                                               4633.5 - 4760.0 METRES
                                                                                         Filter:                                              0
                                                                                                                                             32
                                                                                                                                   0



                                                                                                                                                  0




                                                                                                                                             32
                                                         0.00


                                                                 0.30


                                                                        0.60


                                                                               0.90


                                                                                      1.20


                                                                                             1.50


                                                                                                    1.80


                                                                                                           2.10


                                                                                                                  2.40


                                                                                                                         2.70


                                                                                                                                3.00




                                                                                                                                              0
                                                   100                                                                                 100


                                                    90                                                                                 90


                                                    80                                                                                 80
                        CORE.COREICPHI1_OBC_1 ()




                                                    70                                                                                 70


                                                    60                                                                                 60


                                                    50                                                                                 50


                                                    40                                                                                 40


                                                    30                                                                                 30


                                                    20                                                                                 20


                                                    10                                                                                 10


                                                     0                                                                                 0
                                                         0.00


                                                                 0.30


                                                                        0.60


                                                                               0.90


                                                                                      1.20


                                                                                             1.50


                                                                                                    1.80


                                                                                                           2.10


                                                                                                                  2.40


                                                                                                                         2.70


                                                                                                                                3.00




                                                                               BEST.DNHR_1 (G/CC)

                    Functions:
                    gasdens                                     : Regression Logs: BEST.DNHR_1, CORE.COREICPHI1_OBC_1, CC: 0.628980
                                                                y = (117.058 - 44.1727*(x))




                                                                                      Page 19
                                            Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



5.1.4.5. SW
  Two approaches were applied to SW determination:

   •   Use 3DEX RV data and process using method developed in-house by BA.
   •   Use M1RX high resolution data from HDIL tool for comparison with 3DEX results. M1RX
       curve is 120-inch depth of investigation and 1-foot sample rate. Note that PGL analysis
       used an incorrect hybrid of M2RX (2-foot sample rate curve) and RV curve from the 3DEX.

  Both methods made use of new SCAL parameters (Table 5.4 and Appendix 3). The previous
  PGL interpretation used defaults a=1, m=n=2. SCAL parameters are interpolated to the
  appropriate confining pressure. An ‘a’ value of 1.1 was used for all zones except the UMR3
  (a=1.2). An ‘m’ value of 1.9 was used for all zones except the UMR3 (m=2.1). An ‘n’ value of
  1.7 was selected for all zones, although there was a range on measured values. The SCAL
  data indicated n=1.61 for UMR1 and 1.79 for UMR3. The 1.7 value is the mid point of this
  range. The LMR ‘n’ value was very low at 1.12, but this was rejected as unlikely. Such a low
  value would increase the hydrocarbon saturation in the LMR, in a zone which did not flow any
  gas on test.

  An RW of 0.075 ohm-m at 140oC was used in the computation of SW. This was obtained from
  a DST1B water sample in 3/29a – 4. The RW value equates to a salinity of 22,500 mg/l NaCl.
  The measurement was presumably made on a water sample using a conductivity meter.
  Laboratory water analysis data are presented in Table 5.5. The equivalent salinity expressed
  as NaCl is approximately 27,500 mg/l. This would give an RW of 0.062 ohm-m at 140oC. RW
  measurements were also made on brine extracted from core samples (Table 5.6). The average
  of the core extract RW is the same as the test water analysis RW. The most reliable
  measurement of RW is by direct meter reading. The measured range is actually quite small in
  this case: the difference between Sw computed using 0.062 ohm-m compared to 0.075 ohm-m
  is approximately 1.5 saturation units (SU). Earlier analysis by PGL had used an RW of 0.035
  ohm-m at 140oC (the same value as quoted in a BP file note on 3/29 – 2 petrophysical analysis,
  author and date unknown). Although this value was corrected to 0.075 ohm-m in the PGL
  report (PGL, 2001), PGL used the 3DEX Rv curve as an RT input to the Indonesia Equation.
  As explained in Section 4.1.2, this approach is not endorsed by BA.

Table 5.5. 3/29a – 4 DST1B Water Analysis

                        Ion                          Concentration mg/l
                         Na                               10340
                          K                                 116
                         Mg                                35.2
                         Ca                                245.4
                         Fe                                 3.2
                         Sr                                175.8
                         Ba                                350.4
                         Cl                               16130
                         Br                                80.02
                        SO4                                  0
                       HCO3                                1075
               Total Dissolved Solids                    28551.02
               Equivalent NaCl salinity                   ~27500
                         PH                                7.25
  Reference: McBride and Cook, 2001.




                                           Page 20
                                              Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Table 5.6. 3/29a – 4 RW from Core Brine Extracts

            Depth, mbrt            Filtrate          RW at 20oC,          RW at 140oC,
                                 Invasion,            ohm-m                 ohm-m
                                  fraction
              4762.55               0.063                0.188                0.048
              4769.25               0.081                0.299                0.077
              4779.44               0.083                0.250                0.064
                                                        Average:              0.063
  Reference: Mitchell, 2001.


  The Indonesia Equation was used to compute effective SW (SWE) from the M1RX log. Since,
  none of the SCAL samples exhibited significant electrical shaliness, with the reservoir shale
  contribution to total conductivity under fully water saturated conditions being under 10% (ICCS,
  2001), the Archie Equation would have yielded the same result. The resulting curve is
  CALC.SWE. CALC.BVW is the unflushed zone volume of water. SWE computed from 3DEX
  data by BA is CALC.SWE_3DEX. SWE_3DEX was computed using the Waxman-Smits-
  Thomas Equation (Page, 2001). The MRIL computed SW is PGL.MRIL_SW. The curves are
  compared on the CPI log (track 14, Enclosure 1). The highest gas saturations, which match
  the core SW, are the MRIL values. The 3DEX SWE matches MRIL gas saturations in thicker
  sands but not in the thinly-bedded UMR2. The HDIL under-estimates gas saturations. As
  noted in Section 5.1.3, the MRIL SW curve represents irreducible SW and is not valid below the
  free water level of 4745m TVDSS.

5.2.   3/29a – 2 Review

  3/29 – 2 was drilled with a water-based mud (WBM). The hole is vertical. The well reached TD
  at 5165m in the Devonian. Log data were re-analysed using the input parameters derived from
  3/29a – 4 SCAL. Log curves were already loaded to Geolog by previous workers and it is
  assumed that the curves have been corrected appropriately.

5.2.1. New Petrophysical Analysis
  Input and calculated curves are plotted on the CPI (Enclosure 3).

5.2.1.1.  VSH
  VSH was computed as a normalised GR, with GR_MA of 24 GAPI and GR_SH of 183 GAPI
  (Figure 5.1) for all zones. Note that this well does not have a LR unit. The computed curve is
  CALC.VSH_GR.

5.2.1.2.    PHIE
  PHIE was calculated from the density log, the resulting curve is called CALC.PHIE. RHO_FL of
  1.0 g/cc for water-base mud was used. Other input parameters are the same as 3/29a – 4. The
  log curve cannot match core porosities because the density log cannot resolve the very thin
  sands (15 to 20cm) in UMR2. Core data are used to replace the porosity curve over the UMR2,
  this curve is CALC.PHIE_WCORE.

5.2.1.3.    SWE
  Input parameters Rw, a, m and n were as 3/29a – 4, and included new SCAL parameters
  (Table 5.4). Note that the previous 3/29 – 2 interpretation used an RW of 0.035 ohm-m instead
  of the preferred 0.075 ohm-m at 140oC. Input RT was the deep induction (ILD) curve. The
  resulting curve is CALC.SWE.

5.2.1.4.   Lower Reservoir Section
  There is very little reservoir potential below the Lower Reservoir in 3/29-2, from 4711m to TD.
  Input parameters used were: RHO_MA 1.66 g/cc, RHO_FL 1.1 g/cc, RHO_SH 2.537 g/cc,



                                              Page 21
                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



DT_MA 55 us/ft, DT_FL 155 us/ft, DT_SH 100 us/ft. Archie parameters as for main reservoir
(Table 5.4).

Specific intervals of potential interest are:

•    Heather Sand from 4711 to 4720m: Tight sand with density porosity less than 5 PU and
     sonic porosity up to 9.6 PU. The interval 4720 to 4724m has slower sonic (from 60 to 90
     us/ft) than the sand immediately above. The slow sonic gives higher apparent porosity, up
     to 16.6 PU, but density porosity is zero (the porosity curve CALC.PHIE_WCORE on
     Enclosure 3 indicates sonic porosity spliced in below top LR, which is optimistic but
     highlights potential thin sands). GR and resistivity are relatively low and cuttings
     descriptions indicate that the lithology may be a soft limestone. All intervals are water-
     bearing assuming the same RW as the main Rhum reservoir (0.075 ohm-m at 140oC).

•    Devonian Sand from 4852 to 4870m MD: The density log is missing over 4840 to 4856m.
     The interval from 4861.5 to 4870.5m (log depth) was cored. Core porosity is in the range
     1.6 to 2.2%, average 1.9%. Core permeability range is 0.02 mD to 0.31 mD, with a
     geometric average of 0.028 mD (all Klinkenberg corrected). Sonic porosity up to 4 PU
     maximum is in line with core data, but average Devonian porosity is very low. The rest of
     the Devonian interval has zero log porosity. SW is 100 SU throughout the Devonian
     interval, assuming the same RW as in the main Rhum reservoir.




                                                Page 22
                                                  Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




6.       LITHOLOGY ANALYSIS

     Core description indicates that all of the cored Rhum reservoir consisted of white fine to medium
     grained sand or dark grey organic-rich pyritic mudstones, with no other significant lithologies.
     Thus a binary sand/shale description matched the actual reservoir lithology. A sand/shale flag
     was required as the net flag, since in this type of HPHT reservoir even low permeability rock
     contributes to gas flow. The sand/shale flag was also developed as part of the RMS geological
     model build for Rhum, and to calibrate seismic attribute maps of sand/shale distribution. The
     log is a continuous flag curve of the form 0 = shale and 1 = sand. This section describes the
     method used to derive the sand/shale flag and QC against core data. The Rhum Field wells
     have very good core coverage: 50% of the gross reservoir interval in 3/29a – 4 is cored and this
     includes the entire gas-bearing zone.

6.1.     Methodology

     The sand/shale flag was obtained from a cross-plot of derivative curves VSH, apparent matrix
     density (RHO_MAA) and total porosity (PHIT). Apparent matrix properties such as RHO_MAA
     are generated in Geolog by the Apparent Matrix Properties module (appmat.lls) to be found
     under Petrophysics/Parameter Picking.

     VSH was computed as described in Section 4, from the GR log only. A plot of GR against
     depth (Figure 6.1) indicates a response difference between the two wells across the reservoir.
     However the VSH from GR is normalized based on sand matrix and shale end-points for each
     well (Figure 5.1), so that the VSH plots should be directly comparable although the GR plots
     are not. The shale baseline is derived from the Kimmeridge Clay above and below the turbidite
     sand intervals.

     Porosity is computed from RHOB alone, matching the resulting output to core porosity data by
     varying RHO_FL. Well 3/29a – 4 cored 93m of 191m gross reservoir (nearly 50 percent of the
     gross reservoir interval). Well 3/29 – 2 had 14m of core in the UMR2 zone only. A plot of
     RHOB against depth (Figure 6.2) indicates a similar response between the two wells across the
     reservoir, and curve normalization was not considered necessary. Note that the high density
     zone in 3/29 – 2 between 4650 and 4700 mTVDSS is a dense pyritic shale below the reservoir
     interval.

     RHO_MAA is computed by Geolog as (RHOB – PHIT*RHO_FL)/(1-PHIT). Required inputs are:

     •    RHO_MA matrix density from core (2.647 g/cc).
     •    RHOB from the density log.
     •    RHO_FL the mud filtrate density (based on match to core data, this varied between 0.39
          g/cc in the gas leg of 3/29a-4 and 1.0 g/cc in the water leg of 3/29-2).
     •    RHO_W is formation water density (1.02 g/cc based on 22,500 mg/l NaCl).
     •    RHO_DSH is dry shale density (2.66 g/cc).
     •    RHO_SH is shale density (2.573 g/cc).

     The apparent matrix photoelectric absorption (U_MAA) is generated by the Geolog appmat.lls
     loglan module. It can be a useful parameter for differentiating minerals in a U_MAA vs
     RHO_MAA cross plot (Doveton, 1994). It is computed as U /(1-PHITapparent) where U is the
     volumetric photoelectric absorption. Figure 6.3 is a crossplot of RHO_MAA vs U_MAA with the
     positions of key minerals indicated. The Z-axis is VSH. Sand points fall between quartz and
     calcite, shale points fall slightly to the right of the main kaolinite-illite field. The shales contain
     finely disseminated pyrite and the iron in the pyrite would increase the U_MAA values (in a
     comparable way to presence of iron-rich chlorite). However, the U_MAA values could be
     shifted to the right due to inaccuracies in the computation parameters. Note that the RHO_MAA
     range for sands and shales is as expected from mineral types.

     The RHO_MAA/U_MAA/VSH cross plot (Figure 6.3) could be used directly to generate a
     sand/shale flag. However, the validity of the U_MAA data was uncertain. An alternative



                                                  Page 23
                                                                                                                                   Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



RHO_MAA/PHIT/VSH cross plot was investigated (Figure 6.4). The VSH colour fill indicates
that shale tends to have RHO_MAA>2.8 and VSH>0.4. There is no PHIT distinction between
sand and shale. The sand/shale flag was generated by drawing a polygon around the shale
points in the region RHO_MAA>2.8, VSH>0.4 and PHIT<0.14, and having Geolog compute a
sand/shale log from this.

Figure 6.1. GR vs Depth Plot: 3/29 – 2 & 3/29a – 4.                                                                                              Figure 6.2. RHOB vs Depth Plot: 3/29 – 2 &
                                                                                                                                                 3/29a – 4.

                                REFERENCE.TVDSS vs. BEST.GR_COR Crossplot                                                                                                                                 REFERENCE.TVDSS vs. BEST.RHOB Crossplot
                                                                       Well: 3_29-2 3_29A-4                                                                                                                                                                         Well: 3_29-2 3_29A-4
                                                                        Range: Intervals                                                                                                                                                                             Range: Intervals
                                                                              Filter:                                            0                                                                                                                                         Filter:                                                                                                0
                                                                                                                               7949                                                                                                                                                                                                                                             8169




                                                                                                                                      220
                                                                                                                           0




                                                                                                                                                                                                                                                                                                                                                                          0



                                                                                                                                                                                                                                                                                                                                                                                         0
                                                                                                                               8169                                                                                                                                                                                                                                             8169




                                                                                                                                                                                                               1.95


                                                                                                                                                                                                                              2.05


                                                                                                                                                                                                                                             2.15


                                                                                                                                                                                                                                                             2.25


                                                                                                                                                                                                                                                                            2.35


                                                                                                                                                                                                                                                                                           2.45


                                                                                                                                                                                                                                                                                                          2.55


                                                                                                                                                                                                                                                                                                                         2.65


                                                                                                                                                                                                                                                                                                                                        2.75


                                                                                                                                                                                                                                                                                                                                                       2.85


                                                                                                                                                                                                                                                                                                                                                                       2.95
                                                                          120


                                                                                  150


                                                                                        180


                                                                                               210


                                                                                                      240


                                                                                                             270


                                                                                                                    300
                                                                                                                                 0                                                                                                                                                                                                                                                0
                                               30


                                                        60


                                                                90
                                       0




                               4400                                                                                        4400                                                                    4400                                                                                                                                                                       4400

                               4450                                                                                        4450                                                                    4450                                                                                                                                                                       4450


                               4500                                                                                        4500                                                                    4500                                                                                                                                                                       4500
    REFERENCE.TVDSS (METRES)




                                                                                                                                                                        REFERENCE.TVDSS (METRES)
                               4550                                                                                        4550                                                                    4550                                                                                                                                                                       4550


                               4600                                                                                        4600                                                                    4600                                                                                                                                                                       4600


                               4650                                                                                        4650                                                                    4650                                                                                                                                                                       4650


                               4700                                                                                        4700                                                                    4700                                                                                                                                                                       4700


                               4750                                                                                        4750                                                                    4750                                                                                                                                                                       4750


                               4800                                                                                        4800                                                                    4800                                                                                                                                                                       4800


                               4850                                                                                        4850                                                                    4850                                                                                                                                                                       4850

                               4900                                                                                        4900                                                                    4900                                                                                                                                                                       4900
                                                                          120


                                                                                  150


                                                                                        180


                                                                                               210


                                                                                                      240


                                                                                                             270


                                                                                                                    300
                                               30


                                                        60


                                                                90




                                                                                                                                                                                                               1.95


                                                                                                                                                                                                                              2.05


                                                                                                                                                                                                                                             2.15


                                                                                                                                                                                                                                                             2.25


                                                                                                                                                                                                                                                                            2.35


                                                                                                                                                                                                                                                                                           2.45


                                                                                                                                                                                                                                                                                                          2.55


                                                                                                                                                                                                                                                                                                                         2.65


                                                                                                                                                                                                                                                                                                                                        2.75


                                                                                                                                                                                                                                                                                                                                                       2.85


                                                                                                                                                                                                                                                                                                                                                                       2.95
                                       0




                                                                 BEST.GR_COR (GAPI)                                                                                                                                                                                 BEST.RHOB (G/C3)

                                       Well Legend:                                                                                                                                                            Well Legend:
                                             3_29-2                3_29A-4                                                                                                                                           3_29-2                                     3_29A-4




Figure 6.3. Crossplot – RHO_MAA vs U_MAA:                                                                                                        Figure 6.4. Crossplot – PHIT vs RHO_MAA:
3/29a – 4 Reservoir                                                                                                                              3/29 – 2 and 3/29a – 4 Reservoir

                                 LITH.RHO_MAA_1 vs. LITH.U_MAA_1 Crossplot                                                                                                                                     LITH.RHO_MAA vs. LITH.PHIT Crossplot
                                                                     Well: 3_29A-4                                                                                                                                                                          Well: 3_29-2 3_29A-4
                                                               4633.5 - 4894.0 METRES                                                                                                                                                                        Range: Intervals
                                                                         Filter:                                                 0                                                                                                                                 Filter:                                                                                                  0
                                                                                                                               6438                                                                                                                                                                                                                                       7480
                                                                                                                                                                                                                                                                                                                                                                  47
                                                                                                                       0



                                                                                                                                      2




                                                                                                                                                                                                                                                                                                                                                                                     0



                                                                                                                               6440                                                                                                                                                                                                                                       7527
                                                                                                                                                                                                       0.000


                                                                                                                                                                                                                      0.030


                                                                                                                                                                                                                                     0.060


                                                                                                                                                                                                                                                    0.090


                                                                                                                                                                                                                                                                    0.120


                                                                                                                                                                                                                                                                                   0.150


                                                                                                                                                                                                                                                                                                  0.180


                                                                                                                                                                                                                                                                                                                 0.210


                                                                                                                                                                                                                                                                                                                                0.240


                                                                                                                                                                                                                                                                                                                                               0.270


                                                                                                                                                                                                                                                                                                                                                              0.300
                                                       10.0


                                                                15.0


                                                                          20.0


                                                                                 25.0


                                                                                        30.0


                                                                                               35.0


                                                                                                      40.0


                                                                                                             45.0


                                                                                                                    50.0




                                                                                                                                 0                                                                                                                                                                                                                                          0
                                       0.0


                                               5.0




                               2.500                                                                                       2.500                                           2.500                                                                                                                                                                                      2.500

                               2.555                                                                                       2.555
                                                                                                                                                                           2.575                                                                                                                                                                                      2.575
                               2.611           ORTHOCL                                                                     2.611
                                                                                                                                                                           2.650                                                                                                                                                                                      2.650
                               2.666         QUARTZ                                                                        2.666
  LITH.RHO_MAA_1 (G/C3)




                                                                                                                                                  LITH.RHO_MAA (G/C3)




                               2.722                                                                                       2.722                                           2.725                                                                                                                                                                                      2.725
                                                          CALCITE

                               2.777                                                                                       2.777
                                                                                                                                                                           2.800                                                                                                                                                                                      2.800

                               2.832                                                                                       2.832
                                                     DOLOM                                                                                                                 2.875                                                                                                                                                                                      2.875
                               2.888                                                                                       2.888

                                                SMECTITE                                                                                                                   2.950                                                                                                                                                                                      2.950
                               2.943                                                                                       2.943

                               2.998                          ANHYDR                                                       2.998                                           3.025                                                                                                                                                                                      3.025
                                              KAOLIN
                               3.054                                                                                       3.054
                                                       ILLITE                                                                                                              3.100                                                                                                                                                                                      3.100
                               3.109                                                                                       3.109
                                                                       CHLORITE
                                                                                                                                                                           3.175                                                                                                                                                                                      3.175
                               3.165                                                                                       3.165

                               3.220                                                                                       3.220                                           3.250                                                                                                                                                                                      3.250
                                                                                                                                                                                                       0.000


                                                                                                                                                                                                                      0.030


                                                                                                                                                                                                                                     0.060


                                                                                                                                                                                                                                                    0.090


                                                                                                                                                                                                                                                                    0.120


                                                                                                                                                                                                                                                                                   0.150


                                                                                                                                                                                                                                                                                                  0.180


                                                                                                                                                                                                                                                                                                                 0.210


                                                                                                                                                                                                                                                                                                                                0.240


                                                                                                                                                                                                                                                                                                                                               0.270


                                                                                                                                                                                                                                                                                                                                                              0.300
                                                       10.0


                                                                15.0


                                                                          20.0


                                                                                 25.0


                                                                                        30.0


                                                                                               35.0


                                                                                                      40.0


                                                                                                             45.0


                                                                                                                    50.0
                                       0.0


                                               5.0




                                                                 LITH.U_MAA_1 (B/C3)                                                                                                                                                                          LITH.PHIT (V/V)

                                  0                                                                                        1                                                                       0                                                                                                                                                                  1
                                                                Color: LITH.VSH_GR_2                                                                                                                                                                   Color: LITH.VSH_GR
                                                                                                                                                                                                       Well Legend:
                                                                                                                                                                                                             3_29-2                                    3_29A-4




                                                                                                                                Page 24
                                                                                                             Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



     The key discriminant in the cross plot method is RHO_MAA. The 2.8 g/cc cut off point is
     confirmed by plotting RHO_MAA for both wells as a histogram (Figure 6.5). Note that the high
     density ‘tail’ in the 3/29a – 4 distribution is a shale unit not present in 3/29 – 2. The VSH
     distribution is diffuse although showing a clear trend (Figure 6.6) and a VSH cut-off alone will
     not separate sand from shale. As stated above, PHIT does not differ sufficiently between sand
     and shale. This is because many of the thinly interbedded sands are tightly cemented with
     quartz and are low porosity.

Figure 6.5. RHOB Histogram: 3/29 – 2 & 3/29a – 4.                                                                           Figure 6.6. RHO_MAA vs VSH Cross Plot:
                                                                                                                            3/29 – 2 & 3/29a – 4.

              Frequency Histogram of LOG_LITH.RHO_MAA_1                                                                                                    LITH.RHO_MAA vs. LITH.VSH_GR Crossplot
                           Well: 3_29-2 3_29A-4                                                                                                                                         Well: 3_29-2 3_29A-4
Intervals: KCF, UR, INTER RES SHALE, IRS, UMR1, UMR2, UMR3, LMR, LR                                                                                                                      Range: Intervals
                                   Filter:                                                                                                                                                     Filter:                                           0
                                                                                                                                                                                                                                               7527




                                                                                                                                                                                                                                         0



                                                                                                                                                                                                                                                      0
                                                                                                                                                                                                                                               7527




                                                                                                                                                           1.00


                                                                                                                                                                   0.90


                                                                                                                                                                          0.80


                                                                                                                                                                                 0.70


                                                                                                                                                                                           0.60


                                                                                                                                                                                                   0.50


                                                                                                                                                                                                          0.40


                                                                                                                                                                                                                 0.30


                                                                                                                                                                                                                        0.20


                                                                                                                                                                                                                               0.10


                                                                                                                                                                                                                                      0.00
                                                                                                                                                                                                                                                 0
 0.045                                                                                                       1.0                                   2.500                                                                                     2.500

 0.040                                                                                                       0.9
                                                                                                                                                   2.575                                                                                     2.575
                                                                                                             0.8
 0.035
                                                                                                                                                   2.650                                                                                     2.650
                                                                                                             0.7
 0.030




                                                                                                                             LITH.RHO_MAA (G/C3)
                                                                                                                                                   2.725                                                                                     2.725
                                     2.8 g/cc cut off                                                        0.6
 0.025
                                                                                                             0.5                                   2.800                                                                                     2.800
 0.020
                                                                                                             0.4
                                                                                                                                                   2.875                                                                                     2.875
 0.015
                                                                                                             0.3
                                                                                                                                                   2.950                                                                                     2.950
 0.010
                                                                                                             0.2

 0.005                                                                                                                                             3.025                                                                                     3.025
                                                                                                             0.1

 0.000                                                                                                       0.0
                                                                                                                                                   3.100                                                                                     3.100
              2.56



                       2.64



                              2.72



                                          2.80



                                                      2.88



                                                               2.96



                                                                          3.04



                                                                                   3.12



                                                                                           3.20



                                                                                                      3.28




                                                                                                                                                   3.175                                                                                     3.175

         Statistics:                                                  Wells:                                                                       3.250                                                                                     3.250
                                                                                                                                                           1.00


                                                                                                                                                                   0.90


                                                                                                                                                                          0.80


                                                                                                                                                                                 0.70


                                                                                                                                                                                           0.60


                                                                                                                                                                                                   0.50


                                                                                                                                                                                                          0.40


                                                                                                                                                                                                                 0.30


                                                                                                                                                                                                                        0.20


                                                                                                                                                                                                                               0.10


                                                                                                                                                                                                                                      0.00
         Possible values                            7311              1. 3_29-2
         Missing values                              477              2. 3_29A-4
         Minimum value                           2.50260
         Maximum value                           3.19926                                                                                                                                LITH.VSH_GR (V/V)
         Range                                   0.69666

         Mean                                    2.88086                                                                                                   Well Legend:
         Geometric Mean                          2.87660                                                                                                        3_29-2              3_29A-4
         Harmonic Mean                           2.87234

         Variance                                 0.02444
         Standard Deviation                       0.15634
         Skewness                                -0.03456
         Kurtosis                                 1.63642
         Median                                   2.89515
         Mode                                     2.67200




 6.2.           Validation

     The core descriptions included a number of facies, but on inspection these turned out to be
     either sand or shale. The core description was coded and loaded to Geolog. A visual
     comparison with core description indicated that sand/shale in the core description was matching
     the sand/shale log. In addition, sand thicknesses were computed for the cored reservoir zones
     and compared to the log-derived sand. Results are as tabulated below (Table 6.1). In order to
     put the differences in perspective, the changes to gas initially in place (GIIP) are indicated.


 Table 6.1. Comparison of Core vs Log Defined Sands

                        Well &                                Gross                        Core                    Log Sand                           Interval                          Percentage
                       Interval                              Interval,                     Sand                    Count, m                             GIIP,                           Change in
                                                                m                         Count, m                                                      bcf                               GIIP, %
                       3/29-2:
                        UMR2                                     15                               8                    9                                          92                              + 1.0
                       3/29a-4:
                       UMR1L                                     28                               20                   17                                     630                                 - 8.0
                        UMR2                                     21                                5                    2                                     92                                  - 4.7
                        UMR3                                     13                               11                   11                                     169                                   0
                         LMR                                     29                               22                   20                                     284                                 - 2.2

                                                                                                             Page 25
                                              Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



  Core and log-derived lithologies are displayed on Enclosures 1 and 3. A reasonable match
  was seen in all cored zones except for the UMR2 in 3/29a – 4. The core to log match is
  proportional to sand bed thickness. UMR3 is predominantly sandy with beds 0.5m to several
  metres thick. UMR1L and LMR are thinly interbedded sand and shale zones, with sand beds
  thicker than 25 cm to greater than 1m. The UMR2 in 3/29 – 2 has 80 percent of sand beds
  thicker than 10 cm, with most beds 15cm to 20cm. Within the shales there are very thin (<1cm)
  sands that will not be seen by the logs. The density log in 3/29 – 4 UMR2 fails to resolve the
  very thin sand beds (predominantly less than 10 cm thick in core) and sees predominantly shale
  (Figure 6.7). On Figure 6.7 the core sand grain density in track 3 matches RHO_MAA in sand
  beds in the zones above and below UMR2. However in UMR2 the RHO_MAA consistently
  indicates shale and does not meet any of the sand grain density points except in the thickest
  bed. Note that the neutron/density curves in track 2 only show crossover at the thickest bed.
  Tracks 6 and 7 illustrate the log and core derived sand/shale flag. The thicker black lines in
  track 7 are thin sands in the core that are below display resolution. For interbedded UMR1L
  and UMR3 zones and UMR2 in 3/29 – 2, an error bar of +/-15% may be appropriate. However,
  some of this error will be caused by the difficulty of exactly depth-matching core to log in thinly
  interbedded units as well as log resolution issues. In sandy units (UMR3) the lithology flag
  works very well. The main reservoir in Rhum is the UMR1L and UMR3. The lithology flag will
  not indicate sand where bed thickness is less than 10 cm.

  In order to refine the sand/shale log further, over cored intervals the core sand/shale description
  was overwritten in the sand/shale log. In 3/29 – 2 this is the UMR2 description and in 3/29a – 4
  this is the UMR1L, UMR2, UMR3 and lower part of the LMR (50% of the entire reservoir
  interval). This effectively solves the problem of log resolution in the UMR2 zone since this is the
  only reservoir zone with sand beds below log resolution.

  Core lithology descriptions are stored in Geolog as CORE_LITH.CORE_LITH. Log-derived
  lithology is stored as LOG_LITH.LOG_LITH.


Figure 6.7. 3/29a – 4 UMR2 Zone Log Resolution

     1         2         3            4            5         6        7




                                             Page 26
                                                    Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




7.       PERMEABILITY ANALYSIS

     Descriptions of available core analysis data are included in the Appendices (Appendix 2 and
     3). It is recommended that these Appendices are read carefully before using core-derived
     permeability data stored in Geolog because the data are of variable quality. Permeability data
     in 3/29 – 2 are Klinkenberg-corrected air values. In 3/29a – 4 permeability data are fully
     corrected for reservoir conditions, using the equation:

     Kreservoir =
     Kklinkenberg * ((deviatoric stress/test pressure) ^ (-0.1294 + 0.02028 * LnKklinkenburg))

     The ‘best’ set of permeability          data     in   Geolog   for   3/29a   –   4   is   in   the   set
     GASPERMS.K_GAS_CORR.

     Core poroperm cross plots are included (Figure 7.1 and 7.2). Poroperm transforms are:

                 Well                                          Transform
               3/29 – 2                         K, mD = 10**(-2.13677 + 27.6912*(PHIE))
              3/29a – 4                         K, mD = 10**(-1.97738 + 29.0513*(PHIE))

     PHIE is a decimal. The transforms quoted above are adequate for permeability log generation,
     but the 3/29a – 4 transform gave anomalously high value spikes in places. A multiple
     regression transform was substituted for the simple regression in order to remove the
     anomalies. The regression equation is:

     K, mD = 10**(-7.08097 + 0.0538037DT + 0.00299236RT + 0.310255PE + 21.1147PHIE).

     This relationship gave a fit to core data similar to the simple transform (Figure 7.3).

     For the IRMS model input a maximum upper limit of 1500 mD was applied to the permeability
     logs (maximum permeability in core was 1300 mD). All shale values were set to 0.0001 mD.




                                                 Page 27
                                                                                                                                                            Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 7.1. 3/29 – 2 Poroperm Relationship



                         CORE.CKHL_2 vs. CORE.CPOR_OBC_1 Crossplot
                                                                Well: 3_29-2
                                                          4508.0 - 4688.5 METRES
                                                                    Filter:                                                     0
                                                                                                                               33




                                                                                                                      0


                                                                                                                                    0
                                                                                                                               35
                                0.000


                                         0.030


                                                 0.060


                                                          0.090


                                                                  0.120


                                                                          0.150


                                                                                  0.180


                                                                                          0.210


                                                                                                  0.240


                                                                                                          0.270


                                                                                                                  0.300
                                                                                                                                2
                        10000                                                                                             10000




                         1000                                                                                             1000
     CORE.CKHL_2 (MD)




                          100                                                                                             100             Poroperm Transform:

                          10                                                                                              10
                                                                                                                                          Kh, mD = 10**(-2.13677 + 27.6912* PHIE)
                                                                                                                                          - porosity is a decimal
                           1                                                                                              1

                                                                                                                                           Note: This was used to generate
                          0.1                                                                                             0.1
                                                                                                                                           permeabilities in this well only.
                                0.000


                                         0.030


                                                 0.060


                                                          0.090


                                                                  0.120


                                                                          0.150


                                                                                  0.180


                                                                                          0.210


                                                                                                  0.240


                                                                                                          0.270


                                                                                                                  0.300




                                                         CORE.CPOR_OBC_1 (V/V)

 Functions:
 coreporoperm                           : Regression Logs: CORE.CPOR_OBC_1, CORE.CKHL_2, CC: 0.903804
                                        y = 10**(-2.13677 + 27.6912*(x))




                                                                                                                                        Page 28
                                                                                                                                                         Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 7.2. 3/29a – 4 Poroperm Relationship



ASPERMS.K_GAS_CORR_1 vs. CORE.COREPHIH1_OBC_1 Crossplot
                                                                     Well: 3_29A-4
                                                               4633.5 - 4894.0 METRES
                                                                         Filter:                                             0
                                                                                                                           107




                                                                                                                 0



                                                                                                                                 0
                                                                                                                           123




                                                                           10.0


                                                                                  12.0


                                                                                         14.0


                                                                                                16.0


                                                                                                       18.0


                                                                                                              20.0
                                                                                                                            16
                                          0.0


                                                 2.0


                                                       4.0


                                                               6.0


                                                                     8.0
                                   1000                                                                              1000
     GASPERMS.K_GAS_CORR_1 (V/V)




                                   100                                                                               100


                                                                                                                                         Poroperm Transform:
                                    10                                                                               10

                                                                                                                                         Kh, mD = 10**(-1.97738 + 0.290513* PHIE)
                                     1                                                                               1
                                                                                                                                         - porosity in %

                                    0.1                                                                              0.1
                                                                                                                                         Note: This relationship was not used to
                                                                                                                                         generate permeabilities in the IRMS
                                                                                                                                         model. Instead a multiple regression was
                                   0.01                                                                              0.01
                                                                           10.0


                                                                                  12.0


                                                                                         14.0


                                                                                                16.0


                                                                                                       18.0


                                                                                                              20.0
                                          0.0


                                                 2.0


                                                       4.0


                                                               6.0


                                                                     8.0




                                                             CORE.COREPHIH1_OBC_1 ()                                                     made, fitting core data to a suite of log
 Functions:
 poroperm                                       : Regression Logs: CORE.COREPHIH1_OBC_1, GASPERMS.K_GAS_CORR_1
                                                                                                                                         curves.
                                                0.802344
                                                y = 10**(-1.97738 + 0.290513*(x))




                                                                                                                                     Page 29
                                                                                                                                     Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 7.3. 3/29a – 4 Log Permeability Compared with Core Permeability



                          CORE.COREKH1_1 vs. CALC.K_LOG_1 Crossplot
                                                          Well: 3_29A-4
                                                    4630.5 - 4897.0 METRES
                                                              Filter:                                     0
                                                                                                         114




                                                                                               6



                                                                                                               0
                                                                                           10000
                                                                                                         133




                                                                                  1000
                                 0.01




                                                                         100
                                                                                                         13
                                             0.1




                                                               10
                         10000                        1                                            10000




                          1000                                                                     1000




                                                                                                                         Poroperm Transform:
     CORE.COREKH1_1 ()




                           100                                                                     100




                            10                                                                     10
                                                                                                                         Kh, mD = 10**(-7.08097 + 0.0538037DT
                                                                                                                         + 0.00299236RT + 0.310255PE +
                                                                                                                         21.1147PHIE)
                             1                                                                     1




                           0.1                                                                     0.1




                          0.01                                                                     0.01
                                                                                           10000
                                                                                  1000
                                 0.01




                                                                         100
                                             0.1




                                                               10
                                                      1




                                                     CALC.K_LOG_1 (MD)

 Functions:
 test                                   : Regression Logs: CALC.K_LOG_1, CORE.COREKH1_1, CC: 0.818829
                                        y = 10**(-0.0074497 + 0.955859*log10(x))




                                                                                                                   Page 30
                                                 Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




8.       PRESSURE ANALYSIS AND FREE WATER LEVEL

     Valid RFT, RCI and FMT pressure points are tabulated below (Table 7.1).

Table 8.1. Rhum Formation Pressure Data

                                   3/29 – 2                                 3/29a – 4
     Formation       MD, m       TVDSS, m       RFT, psi       MD, m       TVDSS, m         FMT or
                                                                                           RCI, psi
     KCF               -             -             -           4633.5        4605.5        12353.92
     UR              4539.0        4515.5       12296.00       4666.7        4638.9        12369.26
     UMR1            4565.0        4541.5       12281.00       4692.0        4664.8        12381.16
     UMR3              -             -             -           4760.0        4732.8        12412.40
     LMR               -             -             -           4773.0        4806.3        12500.00
     LR                -             -             -           4834.0        4854.2        13300.00
     Devonian        4852.0        4828.0       12456.00         -             -              -
     Devonian        4862.0        4838.0       13493.00         -             -              -


     The pressure data in 3/29a – 4 are plotted on the attached figure (Figure 8.1). A gas gradient
     of 0.151 psi/ft can be defined. Forcing a water gradient of 0.433 psi/ft through the uppermost
     FMT Run 1 pressure point in the LMR gives a water and gas gradient intercept at 4745m
     TVDSS, defining the free water level (FWL). The FWL is the elevation of the gas-water contact
     free of capillary effects, i.e. the level of the fluid contact in a very wide borehole. It can be
     defined as the depth in the reservoir where the pressure in the gas phase is equal to the
     pressure in the water phase. In the reservoir, the fluid contact as indicated by electric logs (the
     gas-water contact or GWC) may be shallower because of capillary effects in the reservoir rock
     giving higher water saturations above the free water level. On test, free water will not be
     produced above the FWL. Gas gradients of 0.145 psi/ft were computed from PVT analysis of
     gas density and 0.139 psi/ft from the difference between downhole gauge and wellhead
     pressure. In 3/29 –2 a gas gradient of 0.17 psi/ft can be fitted to three FIT pressure points in
     the gas leg (Figure 8.2). This figure also illustrates the rapid pressure increase in the water leg
     with depth (Watts, 2002). Both the reservoir and surrounding formations are overpressured.
     Overpressure in the envelope formations is higher than in the reservoir, with estimated
     gradients as high as 0.85 psi/ft.

     In 3/29-2 there is gas-down-to (GDT) base reservoir, at 4689mBRT or 4651mTVDSS. Note the
     TVDSS in the well evaluation report (4664m) is wrong and assumes a vertical well. The relative
     position of the reservoir and FWL in the two Rhum wells is illustrated by Figure 8.3.

     Modelling of direct core water saturation data gave a FWL of 4744mTVDSS, in very close
     agreement with the formation pressure data (Mitchell, 2001).

     Hydrocarbon shows while drilling 3/29a – 4 were generally poor and do not help in defining the
     FWL (Watts, 2001).




                                                Page 31
                                                             Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 8.1. 3/29a – 4: RCI and FMT Formation Pressure Plot


                          3/29a-4 Formation Pressure Plot (All Runs)
              4660.0




              4680.0




              4700.0          UMR 1
                               Gas gradient 0.151 psi/ft or 0.411 gm/cc
                                             T                R1
                               fit through FM run1 points UM and UM     R3
              4720.0


                                 UMR 3
              4740.0
                                  Contact 4745.1m TVDSS 4773.1m MD
 Depth (m tvdlat)




              4760.0

                                        LMR

              4780.0

                                       Water gradient set at 0.433 psi/ft
                                                          T
                                       Forced through FM run1 point in LM R                     T
                                                                                              FM run 1
              4800.0                                                                          RCI run 1
                                                                                              RCI run 2
                                                                                              RCI run 3
                                              LR                                                T
                                                                                              FM run 2
              4820.0                                                                            T
                                                                                              FM run 3
                                                                                              RCI 4&5 Data
                                                                                              Gas Gradient
                                                                                              Water Gradient
              4840.0


                                                                                                        LR
              4860.0
                  12300.0 12400.0 12500.0 12600.0 12700.0 12800.0 12900.0 13000.0 13100.0 13200.0 13300.0
                                                      Formation Pressure (psi)




                                                            Page 32
                                                                                                                                                 Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



 Figure 8.2. Rhum Field Formation Pressure Plot



                                                                     Rhum Field Formation Pressure Plot
            4480.0
                                                                                                                                                      RFT (3_29-2)
                                                                                                                                                      FIT (3_29-2)
            4530.0
                                                                                                                                                      FMT 1(3_29a- 4)
                                                                                                                                                      RCI 1 ( 3_29a-4)

            4580.0                                                                                                                                    RCI 2 ( 3_29a-4)

                                0.172 psi/ft                                                                                                          RCI 3 ( 3_29a-4)
                              (~Gas Gradie nt )                                                                                                       FMT 2 (3_29a-4)
            4630.0                                                                                                                                    FMT 3 (3_29a-4)
D epth (m tvdss)




                                                                                                                                                      RCI 4 ( 3_29a-4)
                                                                                                                                                      Regional Pressur e Gradient
            4680.0
                                                                                                                                                      Water Gradient

                                                                                          Re gional                                                   Linear ( FIT (3_29-2))
                                                                                         Pres s ure
            4730.0
                                                  FWL @ 4745                              Gradient
                                                                                           1.92 s g
                                                                                                                        Break depth to "proper" over-pressur e trend
            4780.0                                                                                                          in "aquifer" = "regional" pressure ?



            4830.0

                                             Wat er                     Over-pressur e aquifer trend
                                            Gradie nt             (or return to regional "overpressure") ?
            4880.0

                   12100.0   12300.0        12500.0            12700.0         12900.0           13100.0          13300.0         13500.0          13700.0             13900.0      14100.0
            4930.0
                                                                                  Formation Pressure (psi)




                                                                                                             Page 33
                                                                                                                                                                                                                             Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



Figure 8.3. Well Corellation in True Vertical Depth Indicating FWL Position in Reservoir




                                                                                                                                               3/29-2




                                                                                                                                  Reservoir




                                                                                                                                                                                                    LITHOLOGY
                                                                                                                                                            TVDSS
                                                                                                                                                                                  CALC.BVW_1




                                                                                                                                                                    METRES
                                                                                                                                              Zone
                                                                                                                                                                             1        V/V       0
                                                                                                                                                                                  CALC.PHIE_1
                                                                                                                                                                             1         V/V     0
                                                                                                                   GR                                                            CALC.VSH_GR_1
                                                                                                               0   GAPI   250                                                0        V/V       1

                                                                                                                                                            4470

                                                                                                                                                     4476 4475
                                                                                                                                                          4480
                                                                                                                                                            4485
                                                                                                                                  KCF                       4490
                                                                                                                                       32
                                                                                                                                                            4495
                                                                                                                                                            4500
                                                                                                                                                            4505
                                                                                                                                                     4508
                                                                                                                                    UR 4511 4510
                                                                                                                                                            4515
                                                                                                                                   IRS                      4520
                                                                                                                                       20
                                                                                                                                                            4525
                                                                                                                                                            4530
                                                                                                                                                     4532
                                                                                                                                                            4535
                                                                                                                                                            4540

                                  3/29A-4                                                                                        UMR1
                                                                                                                                       29
                                                                                                                                                            4545
                                                                                                                                                            4550
                                                                                                                                                            4555
                                                                                                                                                     4561 4560
                                                                                                                                                            4565
                                                                                                                                 UMR2
                                 Reservoir




                                                                                                                                                            4570
                                                                                                                                       19
                                                                                                   LITHOLOGY




                                                                                                                                                            4575
                                                           TVDSS




                                                                                 CALC.BVW_1
                                                                   METRES
                                             Zone




                                                                            1        V/V       0                                                     4580 4580
                                                                                 CALC.PHIE_1
                                                                                                                                                            4585
                                                                            1         V/V     0
                   GR                                                           CALC.VSH_GR_2                                    UMR3                       4590
                                                                                                                                       21
               0   GAPI   250                                               0        V/V       1
                                                                                                                                                            4595
                                                           4600                                                                                      4601 4600
                                                    4606 4605                                                                                             4605
                                                         4610                                                                                               4610
                                                           4615                                                                                             4615

                                 KCF                       4620                                                                                             4620




                                                                                                                                                                                                                GDT 4651 m in 3/29-2
                                      33                   4625                                                                  LMR                        4625
                                                                                                                                       50
                                                           4630                                                                                             4630
                                                           4635                                                                                             4635
  UR                                                4639 4640                                                                                               4640
                                                           4645                                                                                             4645

                                  IRS                      4650                                                                                      4651 4650
       IRS                            25                   4655                                                                                           4655
                                                           4660                                                                      LR                     4660
                                                    4665 4665                                                                          22                   4665
                                                           4670                                                                                             4670
                                UMR1U
       UMR1U                          18                   4675
                                                                                                                                HEATHER
                                                                                                                                                     4673
                                                                                                                                                            4675
                                                           4680                                                                        10                   4680
                                                    4683
                                                           4685
                                                           4690
       UMR1L                    UMR1L
                                      27
                                                           4695
                                                           4700
                                                           4705
                                                    4710 4710




                                                                                                                                                                                                                GWC 4745 m in 3/29a-4
                                                           4715
                                UMR2                       4720
       UMR2                           22
                                                           4725
                                                           4730
                                                    4732
                                                           4735
       UMR3                     UMR3
                                      13                   4740
                                                    4745 4745
                                                           4750
                                                           4755
                                                           4760
                                                           4765
                                                           4770
       LMR                       LMR
                                      61
                                                           4775
                                                           4780
                                                           4785
                                                           4790
                                                           4795
                                                           4800

                                                    4806 4805
                                                         4810
                                                           4815
                                                           4820
                                                           4825
                                                           4830
        LR                          LR                     4835
                                      59
                                                           4840
                                                           4845
                                                           4850
                                                           4855
                                                           4860
                                                    4866 4865
                                Heather                    4870
                                      10




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                                                 Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




9.       SATURATION-HEIGHT FUNCTIONS

     Water saturation and capillary pressure measurements were made using mercury injection and
     air-brine porous plate methods on preserved core samples from 3/29a – 4 (Cameron, 2001).
     Mercury injection data were also available from 3/29 – 2. The sets of data from the two wells
     were comparable for the same porosity classes. Air-brine measurements were used to
     determine saturation-height functions for a set of porosity classes (Cameron, 2001). The
     derived functions are listed in Table 9.1.


Table 9.1. Saturation-Height Functions Derived from Air-brine Capillary Pressure
Measurements.

                            Rock Type          Saturation-Height Function
                           All rock types         Sw = 0.451703*H-0.233628
                              Φ >10%           Sw = (0.2102*H-0.1518)-0.00481
                            Φ =8-10%           Sw = (0.4169*H-0.2004)-0.00812
                             Φ =6-8%           Sw = (1.1992*H-0.3407)-0.0302
                               Φ <6%           Sw = (1.367*H-0.1507)-0.00159


     The All Rock Types function was used in the non-faulted geological grid RMS model to compute
     water saturation. The four porosity (Φ) class functions were used in the faulted geological and
     simulation RMS models (Southwood, 2001). Irreducible Sw, Swi, was estimated to have a most
     likely value of 0.14 v/v and a potential upside of 0.10 v/v. The ‘H’ term is height in metres above
     the FWL.

     In addition to the functions used in the RMS model, ICCS (2001) subsequently computed single
     saturation – height functions from the same dataset, incorporating Klinkenberg permeability (K)
     and porosity (Φ) into the saturation – height term:

     Sw = 0.943*H – 0.234 * K – 0.265

     Sw = 0.0121*H – 0.167 * Φ – 1.37

     Since the permeability and porosity term is in-built in these equations they should better
     describe water saturation than the terms listed in Table 9.1.

     The various saturation – height curves are plotted on Figure 9.1. This displays the four porosity
     class functions in brown, blue, green and red. The all rock types curve is plotted in pink. This
     overlies the 8 – 10% porosity class curve. Average overall reservoir porosity is 7% (see
     Section 10), so it is reasonable that these curves overlie. The green dashed line is the ICCS
     (2001) curve for a 7% porosity case, and lies between the 6 to 8% and 8 to 10% Cameron
     curves. The ICCS equation and the all rock types equation were input to Geolog and used to
     compute SW. The results are displayed on the CPIs (Enclosures 1 and 3). For 3/29a – 4
     (Enclosure 1) track 14 on the CPI displays log-derived SW (MRIL_SW from the MRIL tool,
     SWE from the HDIL and SWE_3DEX from the 3DEX). Curves are compared with core direct
     SW (COREICSW1). The MRIL_SW and COREICSW1 data show the lowest SW. In fact
     COREICSW1 data appear to be unreasonably low. Note that both these datasets are only good
     above the FWL (see Mitchell, 2001 for discussion of data quality). In track 15 on the CPI the
     COREICSW1 data are compared with two of the model curves: SW_MODEL_ICCS is
     computed from the ICCS (2001) porosity/height/SW equation; SW_MODEL_CAMER is
     computed from the Cameron (2001) all rock types equation. Note that the all rock types
     equation does not have a porosity term and is thus a smooth curve on the log. The two model
     curves show reasonable agreement and also agree with the 3DEX and HDIL-derived SW
     curves. The agreement of model data with log data is reassuring, but the reasons for very low
     core SW data should be investigated further. In 3/29 – 2 (Enclosure 3, track 12) the model
     SW curves give considerably lower SW values than the log SWE curve (whether derived from


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                                                                                    Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



  the LLD or ILD resistivity data). There are no core saturation data available. The discrepancy
  should be investigated further – it may be that the resistivity log data require environmental
  correction or else the SW/height equations should be modified, since in this well the SW/height
  equations give very low SW values in the gas leg.

Figure 9.1. 3/29a – 4 Sw – Height Functions


                                                          Sw-height function (by porosity classes)
                    120
                    110
                    100
                          90
   Height (m) above FWL




                          80
                          70
                          60
                          50
                          40
                          30
                          20
                          10
                           0
                               0   0.1           0.2           0.3            0.4        0.5      0.6            0.7           0.8            0.9      1
                                                                                      Sw (frac)

                                   Phi >10% Sw = 0.2102*(H^-0.1518))-0.00481                            Phi 8-10% Sw = (0.4169*(H^-0.2004))-0.00812
                                   Phi 6-8% Sw = (1.1992*(H^-0.3407))-0.0302                            Phi < 6% Sw = (1.367*(H^-0.1507))-0.00159
                                   Core Data                                                            All rock types Sw = (0.451703*(H^-0.233628))
                                   Phi 7% Sw = (0.0121*(H^-0.167)*(0.07^-1.37))




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                                                Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




10.   ZONE AVERAGES

  Reservoir    zone    averages    are    computed using  the    binary    lithology flag
  LOG_LITH.LOG_LITH_BIN as the net flag. All sand beds are included as net. Averages are
  tabulated below (Tables 10.1 and 10.2).


Table 10.1. 3/29-2 Reservoir Properties

                                       3/29 – 2 Reservoir Properties
                                                                                   Arith.    Geom.
                  Zone Top,    Zone Top,     Gross,            NTG,    Porosity,
        Zone                                          Net, m                       Perm.,    Perm.,
                     m         mTVDSS          m                %         %
                                                                                    mD        mD
        UR          4540        4507          3.4      3.4     100      16.4       669        255
       UMR1         4565        4532          29.2    28.0      96      11.2       250         9
       UMR2         4595        4561          19.4    12.7      65      11.4        85         11
       UMR3         4615        4580          20.9    19.1      91       7.4        14         1
       LMR         4636.5       4601          50.5    44.4      88       2.8         4        0.1
      Totals         -             -         123.4    107.6     87       7.0       100         12
  Note: entire reservoir in gas leg


Table 10.2. 3/29a-4 Reservoir Properties



                                   3/29a – 4 Reservoir Properties
                                                                                   Arith.    Geom.
                  Zone Top,    Zone Top,     Gross,    Net,    NTG,    Porosity,
        Zone                                                                       Perm.,    Perm.,
                     m         mTVDSS          m        m       %         %
                                                                                    mD        mD
        UR         4666.5        4639          1.0     0.5      50       0.5        0.2       0.1
      UMR1U        4692.5        4665         17.9     0.7      4        3.8         3        0.4
      UMR1L         4710         4683         26.8    17.9      67       9.2        70         12
       UMR2        4737.5        4710         22.3     5.0      22       6.9         1        0.5
       UMR3         4760         4732         12.9    10.4      81       6.8        18         1
       LMR          4773         4745         61.0    45.1      74       6.4         4        0.2
        LR        4834.5      4806       47.6         15.4      32       7.1        1.3       0.2
     Totals –
         all         -          -       189.5          95       50       6.8        17        2.5
      zones
     Totals –
                     -          -         81           35       43       7.3        42        6.6
     gas leg
     Totals –
      water          -          -       108.5          60       55       6.6        3.3       0.2
        leg
  Note: gas leg extends from UR to base UMR3.




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                                               Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




11.       RHUM ROCK PROPERTIES

  A rock properties study was conducted to:

      •   Investigate the feasibility of using a lithological impedance (LI) cube to discriminate
          between sand and shale.
      •   Determine how consistent the sand and shale properties are in offset wells.
      •   Determine whether lithology impedance can be used to map variations in reservoir quality
          and hence the distribution of the UMR and the LMR.
      •   Determine whether the gas/water contact is seismically detectable.

  The rock properties study is documented in Keir (2001). The study concluded:

      •   The application of LI maps to discriminate between the UMR and LMR sands and the
          overlying shales is possible but depends very much on the reservoir architecture being
          similar to that of the 3/29a – 4 well. If the reservoir more closely resembles that
          encountered in the 3/29 – 2 well or the properties of the underlying shales are similar to
          those encountered in the 3/29 – 2 well, then application of LI will most probably not allow
          discrimination between sands and shales.

      •   The differentiation of reservoir quality (porosity) is more problematic and probably not
          possible.

      •   The properties of the shales are reasonably consistent in the offset wells, with the
          exception of the 3/29 – 2 well.

      •   Where porosity is high enough (above 10 – 12 PU) the difference between brine-filled
          sands and gas-filled sands should be detectable with changes in acoustic impedance and
          fluid impedance.

      •   The dataset used in the modeling study is of varying vintages, quality and instrument
          technology. Whilst the data has been verified as meeting the QC standards as set by the
          logging contractors, a systematic error could exist which may influence the observed
          differences in rock properties across the field.




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                                              Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005




12.   CONCLUSIONS AND RECOMMENDATIONS

  The Rhum Field gas accumulation was discovered by the 3/29 – 2 well in 1977. Core indicated
  that the reservoir was a thinly-bedded turbidite sequence. In order to resolve and quantify
  reservoir quality in such a thinly-bedded sequence, a comprehensive suite of log data was
  acquired in the subsequent appraisal well 3/29a – 4. The selected logging program was largely
  successful and did improve thin sand definition. It is important to have a range of logging tools
  to address separate but related aspects of reservoir quality. Thus the best tool for determining
  gas saturation and sand volume overall was the MRIL, while individual thin bed quality was best
  measured by high-resolution density logs and the 3DEX tensor resistivity tool. However, the
  3DEX data cannot be interpreted in-house and it is important to involve the logging company in
  job planning, execution and interpretation.

  It was difficult to get a definitive measure of water saturation from log and core data. Core
  saturation data in 3/29a – 4 indicated very low water saturations in the gas leg. Although the
  direct core saturation data agreed with the MRIL saturations, all other data (log SW and
  capillary pressure data) indicated higher water saturations in the gas leg. Core saturation data
  should be reviewed. The importance of good core data cannot be overstated and some
  reservoir features would have gone unnoticed if core had not been available. For example,
  special core analysis of 3/29a – 4 core provided refined Archie parameter values, porosity and
  permeability data corrected for reservoir pressure and overburden, confirmation of formation
  water resistivity and saturation-height data. Very thin, cm-scale, sand beds were seen in core
  that are not detectable on logs but are likely to contribute to production. Given the resolution
  limitations, it may be preferable to perforate the entire gas-bearing zone, from top KCF down to
  the FWL.

  Anomalously high porosities and, consequently, gas saturations, were computed from the
  density log in the LR Zone in a zone that did not flow on test. The MRIL log indicated much
  lower porosity in the same zone. The most likely explanation for the difference is that grain
  densities in the LR are lower than typically encountered higher in the reservoir. Some low grain
  density data points were measured in core plugs in the overlying LMR. However, petrography
  studies failed to identify the nature of the low density material. Core plugs should be re-
  examined in order to rectify this. It would also be worthwhile in future wells to get core over the
  LR to establish if low grain density material exists in this zone also, so that the porosity model
  over the LMR and LR can be refined.

  Reliable pressure data were obtained that define gas and water gradients and a FWL at
  4745mTVDSS. The FWL indicated by formation pressure and core data data is consistent with
  the log data.

  Given the HPHT nature of the gas volume, even low permeability sands are likely to contribute
  to production. Net sand is therefore defined as equivalent to gross sand. Extensive core
  indicates that the reservoir is either fine to medium-grained sand or shale and a simple sand
  flag was devised to describe net, based on matrix density and shale volume.

  Rhum Sand reservoir quality is variable, being generally moderate but ranging from poor to
  good. The highest porosity and permeability was seen in the UR zone of 3/29 – 2, with 100%
  NTG averaging 16.4 PU and 255 mD (zonal averages) in a 3.4m thick sand, but the same sand
  in 3/29a – 4 is only 1m thick with 50% NTG, less than 1 PU and 0.1 mD. The UMR zone ranges
  in porosity between 3.8 and 11.4 PU, permeability 0.5 to 12 mD and NTG 4 to 96%. Individual
  beds in the UMR exhibit Darcy-scale permeability. Despite the variability between reservoir
  zones, the total net reservoir thickness is similar in both wells, being 108m in 3/29 – 2 and 95m
  in 3/29a – 4. All sand was counted as net, using cutoffs of VSH<0.4 and RHO_MAA<2.8 g/cc.

  3/29 – 2 penetrated deeper Jurassic (Heather) and Devonian sand sequences, but these were
  water-bearing and tight. Thus no significant reservoir intervals could be seen on the logs below
  base Rhum Sand.




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                                            Rhum Petrophysical Reservoir Evaluation: v1.0 13/08/2005



13.   REFERENCES

  Baird, T., Fields, T., Drummond, R., Mathison, D., Langseth, B., Martin, A., Silipigno, L. 1998.
  High-Pressure, High-Temperature Well Logging, Perforating and Testing. Oilfield Review,
  Summer 1998.

  Cameron, N. 2001. Rhum Saturation – Height Modelling. Technical File note.

  Doveton, J.H., 1994: Geologic Log Analysis Using Computer Methods.             AAPG Computer
  Applications in Geology, No. 2.

  ICCS, 2001. Petrophysical SCAL Study: Well 3/29a – 4 (Rhum). Phil Mitchell, Integrated Core
  Consultancy Services Limited (ICCS).

  Keir, D. 2001. Rhum Rock Properties. BP, Upstream Technology Group, July 2001.

  McBride, J.J. and Cook, G.E. 2001. Strontium Isotope Residual Salt Analysis (SrRSA) and
  Chemical and Isotope Analysis of DST Waters from Well 3/29a – 4. IAS Limited, May 2001.

  Mitchell, P. 2001. Direct Water Saturation from Core Study: Well 3/29a – 4. ICCS March 2001.

  Page, G. 2001. Rhum Field.         Well 3/29a – 4.      Petrophysical Analysis.     Baker Atlas
  GEOScience. August 2001.

  Paintal, G. 2002. A Petrographical, Reservoir Quality and Fluid Inclusion Characterisation of
  Well 3/29a – 4, and a Quick-Look Petrographical Review and Fluid Inclusion Study of Well 3/29
  – 2, Rhum Field, UKCS. Gautam Paintal, Badley Ashton & Associates Ltd. March 2002.

  Southwood, D. 2001. Rhum Field 3D Geological Modelling and Volumetric Sensitivities.
  ROXAR. October 2001.

  Teeuw, D. 1971. Prediction of Formation Compaction from Laboratory Compressibility Data.
  SPE 2973/SPE Transactions vol 251 September 1971.

  Watts, T. 2001. 3/29a – 4 End of Well Geological Operations Report. BP April 2001.

  Watts, T. 2002. Statement of Requirement - Rhum Development Xmas Tree Rating - Sub
  surface pressures.

  Whitehead, F. 2001. Petrophysical Analysis of Rhum 3/29a – 4.           Production Geoscience
  Limited. February 2001.




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