HYDROCARBON POTENTIAL OF THE VOLTAIAN (VOLTA) SEDIMENTARY by 2yr30pa

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									 HYDROCARBON POTENTIAL OF

             THE VOLTAIAN (VOLTA)

             SEDIMENTARY BASIN

                  GNPC – TEMA; 7TH FEBRUARY, 2007.




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                 Presentation outline
•   ABOUT THE VOLTAIAN SEDIMENTARY BASIN

•   REGIONAL GEOLOGY AND STRATIGRAPHY

•   GEOPHYSICAL AND GEOLOGICAL DATABASE

•   HISTORICAL REVIEW OF OIL & GAS EXPLORATION IN THE VOLTAIAN
    BASIN

•   EFFORTS SO FAR AT GNPC

•   REGULATORY FRAMEWORK

•   HYDROCARBON POTENTIAL

•   DEDUCTIONS AND CONCLUSION.


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        GHANA’S SEDIMENTARY BASINS




                              ONSHORE − 107,100 KM²

                              OFFSHORE – 49,900 KM²




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ABOUT THE VOLTAIAN SEDIMENTARY BASIN
• The Voltaian (or Volta) Basin is the single
  largest sedimentary basin in Ghana. It
  occupies about 40% of the total landmass of
  Ghana, covering about 103,600km2.

• Basin stretches from Ghana into Togo, Benin,
  Burkina Faso and Niger.

• Basin is believed to have a petroleum system
  in place, with favourable conditions for
  generation and accumulation of commercial
  quantities of hydrocarbon.
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   COMPARATIVE SIZE OF VOLTA BASIN WITH
    REST OF GHANA’S SEDIMENTARY COVER
                                              (%)
                                   AREA                  AREA
       AREA       SIZE (km²)                  UNDER
                                 LICENSED             UNLICENSED
                                              LIC.


 Voltaian Basin
                   103,600             0        0       103,600
 (Inland)

Coastal Onshore     3,500              0        0        3,500

  Shelf Region
                   23,000           4,869      21.2     18,131
  (0 – 200m)
 Deepwater
                   26,900          22,127      82.3      4,773
 (200 – 3000m)

    Area Total     157,000         26,996      17.2     130,004

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              REGIONAL GEOLOGY
• Offshore sedimentary basins - formed as a
  result of the separation of the African and South
  American continents.


• The Voltaian Basin is an epicontinental interior
  sag basin associated with the Pan-African
  Orogeny of ~ 600 million years ago and was
  formed as a result of the collision of the West
  African Shield (of the Birrimian System) with the
  Benin-Nigerian Shield (of the Dahomeyan
  System).
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   LITHOSTRATIGRAPHIC SUCCESSION




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                  STRATIGRAPHY
• The basin is an asymmetrical depression filled with thick
  sediments of Late Precambrian (Proterozoic/Infra-
  Cambrian) to Early Paleozoic era. Age differentiation so
  far difficult due to rarity of diagnostic fossils.

• Oldest Voltaian sediments overlie unconformably on
  Lower (“Birrimian”) - Middle (“Tarkwaian”) Proterozoic
  basement rocks.

• Sediment thickness is estimated to exceed 6,000m in the
  deepest portions in the east and south-east.

• Some sediments are considered as young as Devonian-
  Carboniferous in age.
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              STRATIGRAPHY (CONTD.)

• Depositional environment is shallow-marine to
  continental.

• Sedimentation is mainly clastic, with some carbonates.
  The lithology comprises sandstones, siltstones, shales,
  mudstones and limestones. The sandstones are
  massive and conglomeratic in places.


• Sediments, especially lower (older) members, are gently
  folded and with normal block-faulting. Dips recorded in
  Premuase #1 wildcat measured 1 - 4 deg.
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  GEOPHYSICAL & GEOLOGICAL DATABASE
• Aeromagnetic data over the entire the basin, shot
  between 1960 and 2006 (currently as part of EU project):
         • 1960 and 1961 surveys by Hunting Geology & Geophysics Ltd for
           GSD;
         • 1969 surveys by Prakla-Seismos Ag for Uranerzbergbau Gmbh;
         • 1971 survey by CGG for Shell International Petroleum.
         • 2006 (ongoing EU-funded airborne surveys being coordinated by
           GSD).
• Ground Gravity data covering parts of the basin.
• Limited seismic data (208km of 2-D data).
• Shallow Premuase-1 well (1,167m or 3,830 feet) data.
• Limited data on ten (10) hydrodynamic wells drilled to
  ~700m in the 1960s by the Soviets.
• Diverse documentations on various aspects of the
  basin’s geology and geophysics, particularly the ff:

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     GEOPHYSICAL & GEOLOGICAL DATABASE (CONTD.)
• Data currently available at GNPC:
        •     11 individual reports (including on Premuase – 1 well)
        •     16 maps and sections (incl 3 of 4 seismic sections)
        •     7 suites of well logs on sole wildcat, Premuase – 1
        •     Field/Borehole samples including:
                – Washed & dried drill cuttings from 2 locations: Buipe - SGST #7 and
                  Premuase #1;
                – Core chips from 4 locations: Nasia - SGST #5, Tamale – SGST #2,
                  Tibagona – SGST #1 and Yendi – SGST #6.
                – Other field geological/outcrop samples.

• Other data not yet in GNPC domain:
        • Some ~ 31 individual published and unpublished reports.

• Data believed to be in domain of Prof N.A.
  Bozhko/Zarubezhgeologia of Russia:
        • Unspecified reports, sections, maps and other data.

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                      GEOLOGICAL MAP
             (AFTER N.A. BOZHKO, 1964, AND J.E. CUDJOE, 1971 – GSD)




                                      I



  I




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             GEOLOLGICAL CROSS SECTIONS
              (AFTER U. SULUTIU, 1968, AND J.E. CUDJOE, 1971 – GSD)




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                  HISTORICAL REVIEW
• Phase I: Up to 1961- Geological Survey Department (GSD) efforts,
  including P. Davis’ Gravity Survey of 1957 – 58 and early Soviet
  Geological Team’s exploration efforts to determine hydrodynamics
  of the basin.

• Phase II: 1962 - 70 – Soviet Team efforts (till 1965), and later
  Romanian Team’s oil prospecting efforts. Continuation of GSD
  geophysical (mainly gravity) data acquisition.

• Phase III: 1971 - 77 - Efforts by Shell International in magnetic, then
  seismic data acquisitions. Eventual wildcat drilling of Premuase #1
  well.

• Fallow period : 1978 - ~1996 – No significant activity (for ~ 18 yrs.)

• Phase IV (Current): 1996 – Date - Exploration promotion and re-
  evaluation of Basin’s potential by GNPC in cooperation with
  prospective partners, notably Ghana Geological Survey and the
  Mining Sector.
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              HISTORICAL REVIEW (CONTD.)
• Reconnaissance geological mapping by Geological Survey Dept
  (GSD) with detailed mapping in isolated areas.

• 10 hydrogeological wells drilled in the 1960s by the Soviets (SGST
  wells) to average depth of 700m, with some of them encountering
  traces of bitumen, heavy oil and gas indications.

• Ground Gravity data acquisition by Geological Survey Dept in the
  1970s.

• Wide grid aero magnetic survey by CGG in the 1970s, totaling
  18,000 line-kilometers made up of groups of 4 flight lines at 4km
  spacing and 11 tie lines at 45km spacing.

• Only 208 line kilometers of 2D seismic survey by Shell.

• 1 wildcat – Premuase-1 well by Shell in 1977 with results: dry,
  plugged and abandoned.
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              HISTORICAL REVIEW (CONTD.)

• Indications of heavy oil and gas in Soviet (SGST) wells
  of the 1960s. Saline waters (of Cl – Na – Ca type
  mineralization), usually associated with petroliferous
  sediments, were also found in the wells.

• Bitumen was also found impregnated in limestone,
  shale and sandstone sequences, of the Middle Voltaian
  formation.

• Early attempts at evaluating hydrocarbon potential have
  not been successful. Further attempts between 1996
  and early 2000s were also not sustained.

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                 EFFORTS SO FAR AT GNPC
•      In May 2005, GNPC established the Voltaian Project
       Unit (VPU) and charged it with the major objective of
       accelerating and coordinating programmes to promote
       the Voltaian Basin to a marketable status. In
       particular, the VPU was charged to:

     –     Develop strategies of opening up the Voltaian Basin to
           vigorous exploration;
     –     Develop strategies for raising funds for reconnaissance
           survey;
     –     Collaborate with the Ghana Geological Survey to obtain
           applicable set of data from the EU Airborne Surveys;
     –     Develop and implement complementary reconnaissance
           exploration programmes to bring the Basin to a
           marketable status.
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              EFFORTS SO FAR (CONTD)
                   VPU WORK PROGRAMME

• The VPU of GNPC proposed a Work Program and Budget for
  the Basin’s Geoscientific Study and Evaluation. It outlines
  GNPC’s plan to undertake a systematic geologic and
  geophysical study of the Basin within a 4½-year, three-
  phase Study Program.

• Essentially, the Study involves Geological-Geophysical
  Reconnaissance in the initial phase, to be followed by a
  High-grade Evaluation in the second. It will culminate in a
  Drilling/Evaluation programme in the final phase.

• This Study is expected to generate a catalogue of leads,
  prospects, maps, reports and other important technical
  documentation within a broad spectrum of a well-defined
  Petroleum System. Its results are targeted at the
  international petroleum industry and are expected to raise
  the Basin’s status to an attractive and marketable level.
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             EFFORTS SO FAR (CONTD)
Notable efforts currently at GNPC are devoted
   to accomplishing Phase I of the Program.
   However, they also include:

•      Technical contacts, data reviews, etc
       between GNPC and interested investor
       partners and service companies;

•      Compilation and study/review of the basin’s
       data inventory, useful data exchanges with
       GSD, our reliable and dependable partner.
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                EFFORTS SO FAR (CONTD)
• Technical liaison with GSD and by extension, with GEUS (of
  Denmark) through its Technical Advisor (TA) to foster
  familiarization and participation in the Voltaian Study/EDF Project,
  and to identify further channels of technical cooperation.
  Projections have also been made for a joint GNPC - GSD geological
  fieldwork over the basin as a collaborative effort.

• GNPC/GSD Geotraverse Project in 2Q-2006 over the Buem and
  Voltaian geological provinces of Ghana
   – Conducted in collaboration with Prof. Pascal Affaton of CEREGE
     in France.
   – Objective: to collect fresh rock samples for dating to know more
     about the geology of the Voltaian Basin as part of efforts toward
     further investigation.

• GNPC participation in Geosciences workshops, as on the
  Stratigraphy & Water Quality of the Voltaian Basin, organized jointly
  by GSD, HAP (Hydrogeological Assessment Project), GEUS and
  others.

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                 EDF AIRBORNE SURVEYS
•    The EDF (European Development Fund) through its “8 ACP GH 027”
     project has provided financial and technical support to fund a 36-month
     €40m project for Ghana’s Mining Sector Support Programme. GNPC is
     keenly interested in the results of these surveys.

•    Under the Terms of Reference for Airborne Geophysical Surveys, the total
     area to be surveyed includes the Volta River Basin (93,000 km²) and the
     Keta Basin (5,000 km²) totaling 98,000 km².

•    The works are being conducted in 5 phases, with Phases 1 and 2 together
     taking ~12 months:

           • Phase 1: Geological outline through Radar and Optical Satellite
             imageries;
           • Phase 2: Airborne Geophysical Survey for Magnetics, Gamma-Ray
             Spectrometry (and Gravity?);
           • Phase 3: Airborne Electromagnetic and Magnetic Geophysical
             Survey of specific areas, following the completion and
             interpretation of phase 2, using fixed wing Time Domain technology
             – 12 months;
           • Phase 4: Interpretation of the combined Geology and Geophysics –
             9 months;
           • Phase 5: Production of factual and interpretation maps – 3 months.
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         EDF AIRBORNE SURVEY LOCATIONS




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               REGULATORY FRAMEWORK
• The following Laws govern petroleum E & P operations in
  Ghana:

   – GNPC Law (PNDCL 64);
   – Exploration & Production Law (PNDCL 84);
   – Petroleum Income Tax Law (PNDCL 188).

• The above have been conveniently packaged into a Model
  Petroleum Exploration and Production Agreement.

• The elements of the existing fiscal regime are contained in
  PNDC Laws 84 and 188. The fiscal elements are:

   –   Royalty,
   –   Carried Interest,
   –   Additional Interest (Pay Interest),
   –   Petroleum Income Tax, and
   –   Additional Oil Entitlement.
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              REGULATORY FRAMEWORK (CONTD)
Ghana National Petroleum Corporation recommends a
  downward revision of some fiscal elements and an increase
  in exploration period for Voltaian Basin and Deep Water
  operations, and the fixing of same in the Laws. These
  proposals are currently receiving Cabinet attention.


                        Shallow Water            Deep Water          Voltaian Basin


 Royalty                7.5% (from 10%)        5% (Unchanged)         6% (from 10%)

 Carried Interest       10% (Unchanged)        7.5% (from 10%)       7.5% (from 10%)

 Petroleum Income Tax   35% (Unchanged)       35% (Unchanged)       35% (Unchanged)

                            7 Years            10 Years (from 7
 Exploration Period                                               10 Years (from 7 years)
                           (Unchanged)                 years)

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             HYDROCARBON
               POTENTIAL
                 OF THE
             VOLTAIAN BASIN


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              KEY PLAY ELEMENTS
Primary Objective:    Middle Voltaian: Upp
                      Grnsh Gry Sandstone
                      series; Conglomeratic
                      series; possibly
                      Variegated Argillaceous
                      Carbonates.

• Secondary Obj:      Lower Voltaian Oti beds
                      (if fractured).

• Porosity:           Fair, about 10-15% av;
                      Maximum ~ 20%, if
                      fractured.

• Permeability:       Fair.
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              KEY PLAY ELEMENTS (CONTD)

• Source:           Middle Voltaian - Variegated
                    Shale series. Type II, possibly
                    Type III kerogen.

• Seal:             Variegated Shale/Argillaceous
                    Carbonate series.

• Traps:            Structural: Horsts and fault
                    blocks, possibly anticlines.

                    Stratigraphic: possibly
                    pinchouts.
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OVERVIEW OF ANALOGOUS BASINS IN ALGERIA

The following clips are based on a
 presentation, circa 2005, “Contribution
 of the Exploration Activity in
 Renewing the Reserves – the Case of
 Algeria” by Rabih Lounissi of
 Sonatrach, Algeria’s major indigenous
 hydrocarbon institution.


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       ALGERIA - SEDIMENTARY BASINS




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                 PLAY TYPES BY COMPARISON
•   Algeria (Proved case histories)         •   Voltaian (Projected)

     – Objective zones (Reservoirs):              – Objective zones (Reservoirs):
       Є (Pz) thro’ Eoc-Mio (Cz).                   Infra-Є (Vt1) Oti beds thro’ Mid-
                                                    Voltaian (Vt2) Upp Grnsh Gry Sdst.
     – Reservoir lithologies: Mainly              – Reservoir lithologies: Sdst, Congl
       Sdst and Lmst.                               Sdst and Carbonates.

     – Discoveries:                               – Discoveries: Nil (Not yet
        • Oil: Tr, D, O, C, Є, S and K.             applicable).
        • Oil & Gas: Tr, D, O and C.
                                                  – Source rocks: Pz Mid-Voltaian
        • Gas: D, O, Tr, C, S and Є.                Variegated Shales.

     – Source rocks: O, S and D                   – Seals: Pz Mid-Voltaian Variegated
       (Frasnian).                                  Argillaceous Carbonates.

     – Seals: Tr shales.                          – Traps:
                                                      • Structural – Horst blocks,
                                                        Fault traps, possibly
     – Traps: Mainly Structural –                       Anticlines.
       Horst blocks, Fault traps,                     • Stratigraphic: Possibly
       Anticlines; and Stratigraphic.                   pinchouts.
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     ALGERIA – EXPLORATION SUMMARY
• Earliest exploration activities in the Cheliff Basin in the 1890s.

• First commercial discovery in Oued Gueterini Basin in 1948.

• Discovery of Hassi Messaoud and Hassi R’Mel giant fields in 1956.

• Between 1953 and 2004 in Algeria, the following advances were
  made in petroleum E & P:

         • ~ 530,000 km of 2D seismic acquisition – i.e. 0.4 km per km²
           surface area;

         • ~ 6,000 km² of 3D seismic acquisition; and

         • ~ 1,400 wildcats and appraisal wells - i.e. 9 wells per 10,000
           km².

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                   DEDUCTIONS
• On the basis of investigations conducted so far on the
  Voltaian Basin, and based on experience from
  analogous basins that are petroliferous in North
  Africa, South America, and elsewhere, what is the
  outlook for hydrocarbon prospectivity of the Volta
  Basin?

• Clearly, there is a bright and challenging outlook for
  the hydrocarbon prospectivity and future exploration
  potential of the Volta Basin. These stem from fact
  that:

    There really exists a thick sedimentary cover in the
     basin of at least 6km thick in the deepest sections.

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              DEDUCTIONS (CONTD.)
   Structural as well as stratigraphic traps are likely to
    occur in various subsurface locations.

   The occurrence of sandstones and limestones in the
    succession may serve as suitable reservoir rocks.
   On account of the indications of heavy oil and gas,
    bituminous and other hydrocarbon indications that
    were encountered in the 10 SGST wells, this Basin
    most probably harbours favourable conditions for
    the generation and accumulation of commercial
    quantities of hydrocarbon.
   Known oil and gas discoveries already exist in
    analogous basins in North Africa, Brazil and
    elsewhere.

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                 CONCLUDING REMARKS
•The Voltaian Sedimentary Basin has a very bright outlook for its hydrocarbon
exploration. There really exists a thick sedimentary cover of at least 6km in its deepest
sections.

• There must certainly be oil + gas in the Voltaian Basin waiting to be tapped. On
account of the thickness of its sedimentary cover and the bituminous and other
hydrocarbon indications encountered in the Soviet wells of the 1960s, this Basin is
deemed to possibly harbour favourable conditions for generation and accumulation of
commercial quantities of hydrocarbon.

• There are possible structural and stratigraphic leads that could provide favourable
architecture for generation and accumulation of commercial quantities of hydrocarbon.

• The occurrence of sandstones and limestones in the succession, may serve as
suitable reservoir rocks.

• Known oil and gas discoveries and production already exist in analogous basins in
North Africa and elsewhere in the world.

• A very large domestic market for gas and oil in Ghana waits impatiently to be fed from
discoveries and production from the Volta Basin.

• Political, fiscal and legal environments in Ghana provide a lot of incentives for
attracting and sustaining investments in hydrocarbon exploration in the Volta Basin.

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