Skye Asphaltene Dispersant Performance Introduction Skye resin injection by mikeholy

VIEWS: 32 PAGES: 13

									Skye S617
Asphaltene Dispersant Performance

Introduction

Skye S617 is a unique dispersant for asphaltenes and asphaltic oils. Skye S617 is a
proprietary blend designed for Skye Petroleum. This formula has been used by our
chemist in a variety of applications from industrial chemical cleaning to oil field production
enhancement. This report will attempt to outline the various applications for Skye S617
 as well as give examples of the results that can be obtained.
Heavy Oil

The production of heavy oil is a challenge. The oil is thick and flows slowly. Breaking
any emulsions formed is difficult, and because of high viscosity values, the oil carries
sand and other solids. The composition of the oil makes distillation and refining difficult,
and often requires the oil to be upgraded before it is suitable as a feedstock for refining.

                                     What is Heavy Oil?
In simplistic terms heavy oil is oil having an API gravity of between 10 and 20°1, a
viscosity range of 102 to 105 mPa.s, and requires upgrading to make it a suitable feedstock
for refining2. Heavy Oils are found around the world, but the most extensive deposits are
in Northern Alberta and Venezuela. The typical composition of heavy oil includes high
levels of asphaltenes and resins as well as higher than average concentrations of sulphur,
nitrogen and oxygen. The asphaltene content of heavy oils lies in the range of 10 – 26%.
At ambient temperatures heavy crude oils are too viscous to flow. Table 1 shows the
range of distribution differences between light and heavy oils.

                                             o          Resin   Asphaltene
                        Crude                    API                         Asph./Resin
                                                         wt%        wt%
            Canada, Atabasca                8.3        14.0     15.0         1.07
            Venezuela, Boscan               10.2       29.4     17.2         0.58
            Canada, Cold Lake               10.2       25.0     13.0         0.52
            Mexico, Panucon                 11.7       26.0     12.5         0.48
            USA, MS, Baxterville            16.0       8.9      17.2         1.93
            Russia, Kaluga                  16.7       20.0     0.5          0.025
            USA, TX, Hould                  19.7       12.0     0.5          0.04
            Brazil, Campos, Atabasca        19.7       21.55    2.8          0.13
            USA, CA, Huntington Beach       26.2       19.0     4.0          0.21
            Canada, Alberta                 29.0       8.5      5.3          0.62
            USA, LA, Brookhaven             30.6       4.6      1.65         0.36
            Russia, Balachany               31.7       6.0      0.5          0.08
                                            o          Resin   Asphaltene
                        Crude                   API                          Asph./Resin
                                                        wt%        wt%
            Russia, Dossor                 32.6       2.5      0.0          0.00
            Russia, Surachany              35.0       4.0      0.0          0.00
            USA, TX, Mexia                 36.0       5.0      1.3          0.26
            Iraq, Kirkuk                   36.1       15.5     1.3          0.08
            Mexico, Tecoaminocan           36.7       8.8      1.5          0.17
            USA, OK, Ok. City              38.0       5.0      0.1          0.02
            USA, OK, Tonkawa               40.8       2.5      0.2          0.08
            France, Lagrave                43.        7.5      4.0          0.53
            USA, LA, Rodessa               43.8       3.5      0.0          0.00
            USA, PA                        44.3       1.5      0.0          0.00
            Algeria, Hassi Messaoud        45         3.3      0.15         0.05
            USA, OK, Davenport             46.3       1.3      0.           0 0.00
         [Sachanen, 1945; Lichaa, 1977; Garcia, 1989; Altamiran, et al, 1986]

                                  Asphaltenes and Resins

Asphaltenes are the component of heavy oil responsible for
much of the viscosity. By the classical definition, asphaltenes
are the fraction of the crude oil that is precipitated by low
surface tension solvents such as pentane or hexane. The actual
chemical make up of asphaltenes is complex. Asphaltenes do
not crystallise and cannot be separated into narrow fractions by
composition. Thus any evaluation of asphaltenes is a description
of a range of structures and isomers. Postulated structures of
asphaltenes generally illustrate asphaltene as a series of
condensed aromatic rings incorporating sulphur, nitrogen and
oxygen atoms. The actual structure of asphaltenes in a particular      Figure    1   –    proposed
crude oil is undoubtedly a mixture of many molecules ranging
                                                                       structure of asphaltene
in molecular weight from a few hundred grams per mole to
several thousandi.

Resins are the other group of compounds that are precipitated when low surface tension
solvents are added to crude oil. Resins are thought to have structures much like
asphaltenes, but have a lower molecular weight.

The actual physical chemistry of asphaltenes in solution is a matter of debate.
Asphaltenes are thought to exist as colloidal particles surrounded by resins, which act to
provide a transition between the non-polar oil and the polar asphaltenes. One suggestion
is asphaltenes are associated in small clusters bound together by pi cloud interaction
between the aromatic rings that make up the asphaltene moleculesii.
                                      A = Asphaltenes (solute)
                                      R = Resins (dispersant)
                                      a = Small Ring Aromatics (solvent)
                                      s = Saturates (nonsolvent)




A second hypothesis is that asphaltenes are associated with each other because of Van der
Waals forces, and because of their relative insolubility in the bulk solution.

                      Effect of Asphaltenes on the Viscosity of Heavy Oil

In either model the presence of resins in the asphaltene/oil system is critical to the
maintenance of asphaltenes as independent small particles. Asphaltenes contribute to the
viscosity of heavy oil in two ways.

First, asphaltene micelles act as a second internal phase dispersed in the oil. This second
phase increases the viscosity of the system proportionally to the volume occupied by the
phase. Shear (that is flow), changes in temperature and pressure, as well as changes to the
chemistry of the oil due to release of light ends can act to further increase the size of
asphaltene micelles – increasing the viscosity of the oil as it is produced.

Second, asphaltenes and resins are highly polar molecules having a higher affinity for the
water phase of oil field emulsions than the oil. This tends to cause the accumulation of
asphaltenes at the oil water interface of the emulsion droplets – stabilising the emulsions,
and making them difficult to break. The emulsified oil is even more viscous than the
heavy oil itself.


Proposed Mechanism of Action for Skye S-617

Skye S617 is a large organic molecule, with a charged hydrophilic aromatic end,
balanced by a long chained aliphatic hydrophobic end. The molecule is designed to
resemble the resin portion of heavy oil.

Skye S617 acts to improve the stabilisation of asphaltenes and maintain their
dispersion in solution. It does this by providing increased stability to the resin layer of
asphaltene micelles. The S-617 molecule is incorporated into the resin layer and
improves the asphaltene micelle’s dispersability in the oil.

Two effects of S-617 have been observed. The first is a lowering of viscosity. The
viscosity effect usually requires the addition of another solvent such as aromatic naphtha
or diesel fuel. Several possible reasons for this effect can be postulated. Skye S-627
may act to stabilise asphaltene micelles and prevent them from forming aggregates.
Skye S-627 may improve the size of the solvation sphere surrounding asphaltene
micelles, lowering interaction between the micelles, and preventing further
agglomeration. Another possible effect is that Skye S-627 may partially neutralise the
effect of electrostatic condensation.


Results of Lab and Field Testing on Heavy Oil

                                  Case History #1 – Heavy Oil Well

                                           Funnel Viscosities.
Initial screening of the samples showed them to have too high a viscosity for
measurements using either a Fann 35 viscometer or with the DJ scientific viscometer.
This gives a lower limit for the viscosity of the oil at room temperature of over 280 cP.

Because of the high viscosity, the initial screening was performed using a 2-inch funnel.
The retention time of a 25-ml sample was measured and compared between samples.
                     Table 1 Effect of solvent and surfactant addition of oil viscosity



           Additives                                       Retention time           % viscosity
                                                                                    reduction
           None (blank)                                         350 Sec                  0
           500 ppm Skye S -617                                  270 Sec                 22
           1000 ppm Skye S - 627                                190 sec                 45
           1% diesel fuel                                       180 sec                 48
           1% Diesel fuel 500 ppm S-627                          60 sec                 82
           1% Diesel fuel 1000 ppm S-627                         35 sec                 90
           2% Diesel fuel                                       120 sec                 65
           5% Diesel fuel                                        90 sec                 75
           1% Xylene                                            195 sec                 43
           1% Xylene 500 ppm S-627                               35 sec                 90

                                             Pour point tests
Five mls of sample were place in test tubes and heated in a water bath to 35°C. Various
additives were added and the solutions were mixed. The samples were heated to 35°C
and then cooled. The apparent pour point of the mixtures was observed.
               Table 2 Effect of solvent and surfact addition on Apparent pour point



Additives                                                                            Apparent Pour Point
Untreated                                                                                  35°C
1% condensate                                                                              29°C
1% Shell heavy reformate                                                                   25°C
1% Shell Heavy reformate 1000 ppm Skye S -617                                            18°C
2% Shell Heavy reformate 1000 ppm Skye S-617                                           18°C
5% Shell Heavy reformate 1000 ppm Skye S-617                                           <16°
10% Shell Heavy reformate 1000 ppm Skye S-617                                         <16°C

All the samples eventually poured, but it required 4 minutes at a 90° tip for the untreated
and condensate treated samples to slump, even while warm. The samples treated with
reformate, or with reformate and Skye S-617 all had lower pour points, and required
only a few seconds to slump when tipped.

Field Results
The program as outlined was started at approximately 10:00 18/04/2000. The initial
batch of ~800 litres of chemical was applied, followed by the initiation of continuous
injection test.

Petrovera recorded the results of this, and copies of the data recorded are included in
Appendix 1.

                    Table 3 Measured Well conditions before and after chemical injection



                                                             Average          Standard
                                                                              Deviation
          Pump Torque prior to injection                     419 ft-lb        +/- 20
          Pump Torque after injection                        322 ft-lb        +/- 18
          Well Head pressure Prior to injection              742 kPa          +/- 74
          Well head Pressure after injection                 100 kPa          +/- 50

As can be seen from the above table, average pump torque declined by 22% and the
average well head pressure declined by 86%. The close match on the standard deviations
for the pump torque indicates that the pump and well fluids were consistent before and
after treatment. After two days the system suffered a pressure spike and the test was
discontinued.

                            Effect of Treatment on Produced Fluids
Samples of the produced fluids were obtained prior to, and during the injection of
chemical. The samples were analysed to compare the effect of the chemical on the
apparent gravity, viscosity and retained water. The results of the analysis are given
below. The tests were performed independently by Maxxam analytical see appendix II.

                                                       Prior to          After
                                                       treatment         treatment
                API Gravity                            8.8               12.1
                Oil                                    58.49%            83.36%
                Solids                                 7.5%              1.35%
                Water                                  33.84%            14.19%
                Viscosity (cP) @ 30°C                  24182             1942
                 Viscosity (cP) @ 40°C          9044            885
                 Viscosity (cP) @ 50°C          3686            484

The results of these tests confirm the significant difference between the samples of oil
before and after treatment. At 30°C the viscosity of the produced fluid is reduced by
92%. This result is close to the value (90%) predicted by the initial laboratory study.
Significantly, because of the emulsion has broken and the majority of the sand settled out
of the sample the amount of inorganic solids carried in the treated sample is substantially
less than that of the untreated emulsion.

                                      Case History #2

Oil Properties


The submitted samples were analyzed to determine their composition. The results are
shown in table 1.

            Constituent                 A       B        C            D      E
            Water                      11.21    11.6     41.5         13.8   12.1
            Wax                           <5     <3       <4           <1     <1
            Asphaltene                    38    47.3     29.0         37.4     46
            Lighter hydrocarbon           49      36     24.3         46.8   40.9
            Inorganic Residue             <1     <1       <1           <1     <1

Viscosity Studies

Each oil was tested to determine the effect of various surfactants and solvents on the
viscosity profile of the oil. The tests were performed using a Brookfield LV-II
viscometer and the small sample adaptor.
                              Figure 1 Viscosity Vs temperature for sample A




                                                   087-00A


     100000




      10000




       1000
              15       20               25          30             35             40           45     50
                                                     Temperature °C

                            Untreated        1.5% Sterling 7710         093 1% 7710 plus 0.02% 8284



Sterling 7710 is a stabilized solution of Skye S - 617 in Husky Cutter D. Sterling
8482 is an emulsion breaker for heavy oil. The viscosities given are for the range of 25 –
40°C. The viscosities at 21°C can estimated from the graphs.

                       Test                      Extrapolated                  % Viscosity
                                               Viscosity to 21°C               Reduction
              Untreated                              49908.09064                              0
              1.5% 7710                              30326.75624                       39.23479
              1.0% 7710 + 0.1% 8482                  30650.24674                       38.58662

As can be seen the combination of solvent and chemicals can have a significant effect on
the viscosity of the mixture.

Sample B
                                 Figure 2 Viscosity vs temperature for 087-00B




                                         Viscosity Vs Tempertaure 087-00B


     100000




      10000




       1000
              20      25            30           35           40           45           50        55   60
                                                        Temperature (°C)

                                            Untreated        1.5% 7710           1.0% 7710



The viscosities at 21°C can estimated from the graphs.

                          Test                     Extrapolated                   % Viscosity
                                                 Viscosity to 21°C                Reduction
              Untreated                                     69702.51                          0
              1.0% 7710                                     44522.09                   36.12555
              1.5% 7710                                     36957.13                   46.97876

Again a substantial reduction of viscosity could be achieved.


Vacuum Reformer Bottoms

Vacuum Reformer bottoms and other residual oils are the final remnants of the crude oil
distillation process. These products will typically contain a high level of polycyclic
aromatic compounds, asphaltenes and some resins.
The exact composition of these residual materials varies from refinery to refinery,
depending on the desired outcome. The samples examined by the lab were from
residual materials which in one case (Curacao) had no final end use and were placed into
a landfill, and in the second were intended for the manufacture of asphalt.

                           Laboratory Study #1 - Curacao Pit Samples

A series of tests were performed to give a quantitative value for the dissolution rates of various
combinations of solvents and deposit. The results of these tests are given in table 3. Samples of
the sludge were weighed into a beaker and the solvent added on top. The samples were agitated
ever 10 – 15 minutes. After various time intervals the solvent was poured off and the remaining
amount of sludge re-weighed.


                                               Table 4



                Temperature: 20°C                Sample 032B
                Time                            Weight of residue
                                 A                     B                  C
                Initial         30                    35                  25
                1hour           35                    32                  24
                2hours          33                    26                  19

                Temperature: 50°C                Sample 032B
                Time                            Weight of residue
                                 A                     B                  C
                Initial         45                    35                  35
                1hour           41                     5                   9
                2hours          36                     0                   2

                Temperature: 50°C                Sample 032A
                Time                            Weight of residue
                                 A                     D                  B
                Initial         45                    35                  35
                1hour           45                    22                  15
                2hours          40                    15                   2

A-   Diesel Fuel
B-   Diesel Fuel plus 1000 ppm Skye S-617
C-   Diesel Fuel plus 500 ppm Skye S-617, 1000 ppm Skye S-617
D-   Diesel Fuel plus 500 ppm Skye S-617

The results of the dissolution rate study show that the required concentration of Skye S-617
is 1000ppm. Significant differences in the dissolution rates can be seen between the 032A sample
and the 032B sample. (The 032C sample was not tested, as its composition was essentially the
same as the 032A sample). The addition of other surfactants with the S627 was found not to
improve the dissolution rates.
Dissolution Tests

Mixtures of the solids and diesel fuel were prepared by heating the diesel fuel and samples to
75°C and blending them together. In some samples Skye S-617 was added on a concentration
based on the total weight of the sample. Comparisons of the density and viscosity’s of various
samples were then performed. The gravities were determined using method ASTM D-66 and the
viscosity using ASTM-D445. Analyses were all carried out by a third party laboratory.



                                 Table 1 Viscosity versus temperature



Sample 032A
  Wt%        Wt%               ppm S-          API                      Viscosity (cP)
 Diesel     Sample              627           Gravity
  Fuel
                                                                20°C         50°         90°C
         27             73         1000             8.8         431000        4354        168.2
       28.5           71.5         1000            10.6          36863         762         88.5
       27.5           72.5         1500             9.4         293000        3244        134.9
       29.5           70.5            0            10.3          48859         934         98.3

                                 Table 2 Viscosity versus temperature



Sample 032B
  Wt%       Wt%              ppm S-           API                       Viscosity (cP)
 Diesel   Sample              627            Gravity
  Fuel
                                                                 20°C        50°         90°C
        30            70            0              13.2           36548        785          87.2
        30            70         1000              13.3            7408        459          51.2
        30            70         1500              13.2            7093        450            53
      29.5          70.5         2000              13.3            7408        459            51


The results of this study show two trends. First, the resulting mixture viscosity and
gravity is sensitive to the starting sample. Results on the A sample show that
concentrations of diesel fuel below 27.5% are unpractical giving API gravity’s below 10.
Addition of Skye S-617 was observed to give improved dissolution of the sample as
well as improved viscosity’s, however, the effect was small on these high-density
mixtures.

The second effect was observed with the lower gravity sample 032B. This sample when
blended at a 30% diesel concentration showed a marked decrease in final viscosity. The
amount of the effect is seen most dramatically at temperatures below the nominal melting
point of the sample (approximately 85°C). A concentration of 1000 ppm gave a
significant effect, but increasing the amount to 1500 or 2000 ppm did not give any
significant improvement. Concentrations lower than 1000 ppm have not been tried.

Not enough samples remained to conduct further tests.

                  Laboratory Study #2 – Husky Lloydminster reformer Bottom

Evaluation:
The sample was tested to determine its composition and to find the best combination of
surfactants and solvents to aid in dispersing the sludge.

Analysis:

The sample was analyzed to determine its composition the results of the analysis are given in
table 1.

                                              Table 5



                      Constituent                          Weight %
                                                                  062-99
                      Water                             Not determined –
                                                                 present
                      Wax                                           6.75
                      Asphaltenes and resins                        37.8
                      Light Hydrocarbon                             55.5
                      Inorganic residue                               <1

The sludge materials were mixed with various solvents and surfactants and the resulting
properties were observed. The results of the evaluations are given in table 2.




                                              Table 6



Test   Solution                          Observations
I.D.
 1A    1:1 sludge: Diesel fuel           Mixes easily at room temperature (16°C) with slight
                                         agitation. Final viscosity of the mixture is high.
1B     1:1 sludge: Diesel fuel           Mixes easily. Pour point of the mixture ~-6°C.
       500 ppm Skye S-617
1C     1:1 sludge: Diesel fuel           Mixes Easily. Pour point of the mixture is below –20°C
       1250 ppm Skye S 617
1D     2:1 sludge: Diesel fuel           Mixes poorly at room temperature, mixes easily on
                                         heating to 60°C, but solidifies on cooling.
Test     Solution                              Observations
I.D.
 1E      2:1 sludge: Diesel fuel               Mixes easily at room temperature. Pour point of
         1250 ppm Skye S - 617                 mixture <-6°C
 1F      1:1 Sludge (cooled to –5°C):          Mixes poorly. Eventually forms a uniform mixture.
         diesel at 40°C
1G       1:1 Sludge (cooled to –5°C):          Mixes rapidly. Forms a uniform mixture. Pour point
         diesel at 40°C                        <20°C.
         1250 ppm Skye S-617


Viscosity Study

The viscosity versus temperature was measured using a DJ scientific viscometer. The results of
these tests are shown in the graph below.


                                        viscosity vs Temperature

                    700



                    600                                            1:1 diesel +residue
                                                                   1:1 diesel 500 627
                                                                   1:1 diesel 1250 ppm S627
                    500



                    400



                    300



                    200



                    100



                      0
       -10     -5         0     5         10        15      20           25             30    35
                                          temperature °C




Final Cleaning

After the mixing tests were performed. The mixtures were poured out of the test beakers and the
residues were removed using various cleaning solutions.

Test     Solution                              Observations
I.D.
 1A      Water 80°C                        Worked Poorly, with little dispersion
 1B      Water (60°C) 3% Skye D-         Worked slowly.
Test     Solution                          Observations
I.D.
         731
    1C   Water (60°C) 3% Skye D-           Worked fast, lifted the deposit from the glass and metal
         731, 0.25% Skye S-617             surfaces, and maintained dispersion after cooling.



1
 Strom, N.A. and Dunbar, R.B. “Bitumin Resources of Alberta: Converting Resources to Reserves”
Chapter 6 in “ The Future of Heavy Crude and Tar Sands”, Unitar 1981
2
 Unitar Proposal for the Definition of Heavy Crude and Tar Sands and Addendum by Group of Experts,
Second International Conference on Heavy Crude and Tar Sands, Caracas, Venezuala, Febraury 1982, p.2
3
 J.G. Speight “ The Structure of Petroleum Asphaltenes – Current Concepts” Information series 81
Alberta Research Council 1978
4
 Dickie, J.P. and Yen T.F. “Marcostructures of Asphaltic Fractions by Various Instrumental Methods”
Anal. Chem. 1967 39,p1847

5

								
To top