Society of Petroleum Engineers

SPE 26148

Capillary Pressure Characteristics at Overburden Pressure Usingthe Centrifuge MethodA.a. Ajufo, D.H. Daneshjou, and J.D. Warne, Core Laboratories

SPE Members

Copyright 1993, Society of Petroleum Engineers, Inc.

This paper was prapared for presentation at the SPE Gas Technology Symposium held in Calgary, Alberta, Canada, 28-30 June 1993.

This paper was selected for presentation by an SPE Program Committee following review of Information contained in an abstract submitted by the author(s). Contents of the paper,as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflectany position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are sUbject to publication review by Editorial Committees of tha Societyof Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledg­ment of where and by whom the paper is presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A. Telex, 163245 SPEUT.

ABSTRACT

This paper contrasts the results of cenbifuge capillarypressure measurements determined at ambient andoverburden pressures. The effects of cenbifugal forcesand overburden pressure on the integrity of wellconsolidated uniform rock samples are minimal. However,unconsolidated sands, poorly consolidated sandstones,and friable cores are susceptible to deformation and grainre-arrangement, while vuggy cores are susceptible tosurface drainage. The severity of these occurrences,which depend on sample lithology and the magnitude ofcentrifugal forces, can be minimized or avoided by properjacketing and application of overburden pressure.

INTRODUCTION

The theory, measurement1-5 and application6-22 ofcapillary pressure concepts have received extensiveattention in the petroleum industry literature. Theseapplications range from the fundamental use of drainageor imbibition capillary pressure for determination of fluiddistribution, pore size distribution,6-8 and absolutepermeability,6,7,9,10 to the more complex issues of relativepermeability,6,12,14 wettability11, oil recovery13, and theassessment of formation damage and stimulation.15 Thedevelopment and application of the general concepts ofcapillarity were introduced by Leverett1 in 1941. Sinceintroduction, three methods have evolved as the mostwidely used means of obtaining capillary pressure data.

These are the centrifuge, porous plate, and mercuryinjection .

Hassler and Brunner's2 pioneering work introduced thecentrifuge technique for determining capillary pressure andthe methodology for converting the average saturation tothe end-face saturation. Capillary pressure measurementsin the centrifuge have historically been performed on "un­jacketed" samples without overburden pressure. O'mearaet a1. 16 stated that "there are several reasons for jacketingcores: to prevent evaporative losses, to minimize excessfluids from collecting on the outside of the core, and tosafeguard core integrity by protecting the sides andedges". Omoregie17 recommended that for unconsolidatedsamples, "application of overburden pressure with aHassler-cell or by potting in acrylic or other suitablematerial is preferred", and suggested that "more tests bedone to make the results of this overburden pressureeffect quantitatively definitive".

This paper presents the results of centrifuge capillarypressure measurements determined at overburdenpressure conditions. Although the Hassler and Brunner2saturation conversion method was used for this work,different saturation conversion18-21 methods can be usedwithout altering the results of this study. Fundamentally,major factors affecting capillary pressure behavior arewettability, interfacial tension, pore size and distribution,saturation history, and fluid density difference. This workfocuses on the effects of changes in pore siZe anddistribution on capillary, pressure keeping other factors

107

2 CAPILLARY PRESSURE CHARACTERISTICS AT OVERBURDEN PRESSURE USING CENTRIFUGE SPE 26148

constant. The observed changes have significantimplications in the application of capillary pressure data.For example, data indicate overburden pressure canincrease capillary held water saturation and ignoring thiscan result in overestimation of hydrocarbon reserves.

MATERIALS AND EXPERIMENTALPROCEDURES

Equipment

The system (Figure 1) consists of a Beckman centrifugemodified for specially designed hydrostatic core holders.The core holder assem bly places the sample betweenmetal end-pieces within an elastic sleeve which acts as abarrier from the fluid used to exert the hydrostaticconfining pressure. Upon installation in the core holdersand application of requisite overburden pressure, samplescan be cleaned by flow-through miscible solvent injectionand dried by air or aitical point drying. Porosity andpermeability can be measured, followed by saturation withtest fluids. This versatility minimizes handling and preventsstress-cyding due to loading and unloading.

The centrifuge system is capable of accommodatingconfining pressures ranging from 50 psi to a maximum of4000 psi and temperatures ranging from ambient to 160degrees Fahrenheit. When performing elevatedtemperature testing, the core-holder assembly is allowedto reach thermal equilibrium within an oven while theconfining pressure is monitored and maintained at theappropriate level. System fluids are also heated prior tofinal assem bly to prevent uncontrolled pore pressureincreases dUring the centrifuge test. The centrifugechamber is then preheated prior to the initiation of testingto prevent temperature changes in the sample assembly.

Rock Samples

Core samples ranged from friable Bend Conglomerates, tothe well consolidated sandstones from Delaware andBerea formations. The Berea test samples were well­cemented, fine to medium grained sandstones, and theDelaware test samples were also well-cemented, but veryfine to fine-grained sandstones. Bend Conglomerate testsamples were moderately-cemented, coarse to verycoarse grained sandstones.

Fluid Samples

by the centrifuge method is the ability to accommodatedifferent combinations of both reservoir and syntheticfluids. Although this study was carried out using gas-watersystems (air and potassium chloride brine), gas-oil, andoil-water systems (both imbibition and drainage withoutunloading) can also be used.

Capillary Pressure Test Procedures

Core samples were extracted with toluene and methanolusing the soxhlet technique. They were dried to aconstant weight in a humidity controlled oven. Grainvolume was determined using the helium expansion,Boyle's Law method.

Porosity and permeability were determined on theconsolidated samples at a minimum overburden pressureof 800 psi, followed by evacuation and pressure-saturationwith two weight percent potassium chloride (KCI) brine.

For initial reference, measurements were performed withno overburden pressure on selected samples using theporous plate and centrifuge methods. A three-Barceramic plate was saturated with two Weight percent KCIbrine, and saturated samples were placed on the plate,with a double layer of tissue paper to ensure capillarycontact. The sample chamber was pressurized withhumidified air, using pressures ranging from 1 to 35 psi.Equilibrium saturations were determined gravimetrically inthese samples.

Following porous-plate capillary pressure measurements,sample assemblies were loaded into the centrifuge trunion.Air-brine capillary pressure measurements were performedby non-stop centrifugation at increasing rotational speedswhile recording the volumes of displaced fluid. Saturationequilibrium at each speed was determined by monitoringbrine displacement until no change was observed for anysample for a period of at least eight hours. The sampleswere leached with methanol to remove KCI salts, and thepreparation and measurement processes were repeatedfor higher overburden pressure measurements.

Capillary pressure - average water saturation relationshipsin the core were determined from eqUilibrium producedvolumes, using Equations 1 and 2. End-face saturationsfor the centrifuge experiments were calculated using theHassler-Brunner method. The median pore throat size (@50 percent brine saturation) was calculated using Equation3 and Leverett J-function values were obtained byEquation 4.

One of the advantages of determining capillary pressure

108

(1)

SPE 26148 A. AJUFO, D. DANESHJOU, J. WARNE, D. HARVILLE 3

2 2 2Pc =C1 Ap CO (rb - rt ) (2)

r =(2 a cos 9 C2) 1 Pc (3)

J(Sw) = [Cs Pc ( KIt )0.5]1 a cos 9 (4)

Petrographic Analysis Test Procedures

The sample fractions were prepared for thin sectionanalysis at stress from 1_1/2" diameter core plugs. Waferswere cut from the plugs and fitted into a rubber boot of ahigh pressure core holder. Hydrostatic pressure wasapplied to the outside of the rubber boot until a pressure of2200 psi was achieved. An epoxy resin containing a bluedye was injected (under pressure) into the samples. Theinternal epoxy pressure and the outside hydrostaticpressure were inaeased simultaneously until they reached1500 psi and 3700 psi, respectively, resulting in a 2200 psinet overburden. These oressures were maintainedovernight to allow the epoxy to cure.

After removal from the core holder, each of the sampleswas mounted on a frosted glass slide and then cut andground in water to an approximate thickness of 30miaons. The thin sections were analyzed using standardpetrographic techniques. Modal percents of frameworkgrains, cement (and types) and matrix were determined bypoint count (250 points) analysis. In addition, grain sizemeasurements were done on 80 grains to determine meangrain size and sorting.

RESULTS AND DISCUSSION

Capillary Pressure Characteristics

Permeability and porosity values are listed in Table 1 forthe samples tested. Porosity ranges from 15.6 to 23.4percent, while permeability varies from 2.4 to 4810millidarcys. Capillary pressure data obtained by theporous plate and centrifuge methods without overburdenpressure show equivalency on Samples SA and 13A andare presented in Table 1 and Figures 2 and 3. At acapillary pressure of 35 psi, residual water saturation onSample 5A was 16.4 and 14.7 percent pore space byporous plate and centrifuge methods respectively.Similarly, Sample 13A showed residual water saturation of22.3 and 20.2 percent using these two methods. Thisequivalency is consistent with reported results of otherinvestigators.17,22

109

Effects of overburden pressure on capillary pressurecharacteristics for the rest of the samples are shown InTable 2 and Figures 4 to 7. At the maximum displacementpressure of 100 psi, the magnitude of variation in bothaverage and end-face residual water saturations for theconsolidated samples was about 6.0 percent of porespace, the Bend Conglomerate showed a variation of 16.0percent of pore space as a result of inaease inoverburden pressure. The average saturations for all thesamples tested at capillary pressure of 100 psi both atoverburden and non-overburden are presented in Table 3.The average saturations also show smaller stress effecton Berea and Delaware sands and larger impact in Bendconglomerates. Median pore throat radii values werecalculated at 50 percent brine saturation. At overburdenpressure radii values were lower than the valuesdetermined without overburden pressure (Table 4).

Overburden and non-overburden capillary pressure datafor samples 13A and T2 were normalized by calculatingJ­function values. The log-log plots of J-function vs. brinesaturations are presented in Figures 8 and 9. Generalparallel lines in both samples show consistency of capillarypressure measurements at overburden and non­overburden conditions in these samples. The magnitudeof stress effect ( separation of two lines) could be seen insamples 13A and T2. The non-equivalency of the J­function curves shows that overburden pressure effectscannot be accounted for by normalizing porosity andpermeability.

Petrographic Analysis

Delaware sands (samples 35 & 104) are well sorted(Standard Deviation = 0.02) very fine-grained sandstones.Detrital day occurs in trace amounts. Cementation byquartz, dolomite, and feldspar is abundant, but anhydrite,barite, pyrite, anatase, and day minerals are also found aspore-occluding cements. Total cement by point countranges from 20-21%.

Berea samples (T1 & T2) are moderately sorted (StandardDeviation = 0.04) fine to very fine-grained sandstones.Detrital clay matrix is absent, but the samples· are well­cemented by abundant quartz overgrowths, pore-fillingkaolinite, and Fe-dolomite. .Minor amounts of authigenicfeldspar, anatase, siderite, illite, and chlorite are alsopresent. Total cement in these samples averages 15% bymodal point count. Intergranular porosity is the mostcommon porosity type in these Berea sandstones.

Bend conglomerates are poorly sorted (Standard Deviation= 0.47-0.82) coarse-grained sandstones. These samples

4 CAPILLARY PRESSURE CHARACTERISTICS AT OVERBURDEN PRESSURE USING CENTRIFUGE SPE 26148

also contrast to the other two groups by the paucity ofcement in these two samples (avg. 8.2010). Detrital claymatrix is present (0.8-1.6%) but is not seen in significantabundance. Intergranular pores are abundant but exhibit awide variety of pore throat sizes due to the variability ingrain size.

Evaluation of textural and compositional controls onstress-sensitivity is given in Table 5. The most significantfactors are grain size, degree of sorting, and cementation.Larger variance in saturation from ambient to confined at100 psi capillary pressure is seen with inaeasing grainsize and sorting and deaeasing cementation (Table 6).Framework grain composition may be a factor, but notenough variability is seen in this data set. Lack of cementand variability in grain size makes it possible to have re­arrangement of grains under stress. In contrast, highlycemented, well-sorted samples are already packed andIithified to a high degree, resulting in little change understress.

CONCLUSIONS & RECOMMENDATIONS

Test results show that capillary pressure data are affectedby overburden pressure. The degree of sensitivity isshown to be magnified for poorly consolidated, poorlycemented and poor1y sorted rocks.

It is recommend that formation or reservoir stresssensitivity be saeened by determination of porosity andpermeability at multiple overburden pressures.Fundamentally, for constant fluid properties andwettability, these effects are due to alteration of poregeometry and grain re-arrangement.

Application of capillary pressure data determined at non­overburden conditions for rocks susceptible to stress­induced alteration can lead to erroneous decisions.Examples are under estimation of water saturation andhence over estimation of reserves, and over estimation ofparticle sizes selected to reduce sands invasion.

• Capillary pressure data show sensitivity to overburden

pressure.

• The effects of overburden pressure on the pore

geometry of well sorted and well cementedconsolidated test samples were minimal.

• Consolidated core samples with poor sorting and/or low

cementation showed greater sensitivity to overburdenpressure. Consequently, overburden effects on

unconsolidated cores are likely to be significant.Capillary pressure measurements on unconsolidatedcore or poor1y cemented core should be performed atoverburden pressure conditions.

• Capillary pressure data determined by porous-plate and

centrifuge methods without overburden exhibitequivalency.

NOMENCLATURE

J(Sw) = Leverett-J Function, (dimensionless)Koo =K1inkenberg corrected gas permeability, (md)

Pc =Capillary Pressure, (psi)

rb =Outer radius of rotation, (em)r = Pore entry radius, (microns)rt = Inner radius of rotation, (em)8wa =Average water saturation, (fraction)Swr = Residual water saturation, (fraction)

Sw(Pc) = End face water saturation, (fraction)Vp = Pore volume, (cc)

Vwp =Volume of produced water, (cc)

L\p =Density difference, (gm/cm3)Q) =Centrifuge rotational speed4' = Porosity, (percent pore space)(J = Interfacial Tension, (dynes/em)e= Contact Angle, (degrees)C1 =Centrifuge Constant

C2 =Conversion Constant

C3 =Conversion Constant

ACKNOWLEDGMENT

We thank the management of Core Laboratories forpermission to publish this paper. We also thank Mr. DareKeelan, and Dr. Ben Marek for reviewing the manuscript.Thanks also to Brian Nicoud , Drew Dickert, Mark Smesnyand Steve Hoff for helping with measurements.

REFERENCES

1. Leverett, M. C.: "Capillary Behavior in Porous Solids,"Trans.AIME, vol. 142 (1941), pp. 152-169.

2. Hassler, G. L. and Brunner, E.: "Measurement ofCapillary Pressures in Small Core Samples," Trans.,

110

SPE 26148 A. AJUFO, D. DANESHJOU, J. WAANE, D. HARVILLE 5

AIME, (1945),v. 192, 114-123.

3. McCullough, J. J., Albaugh, F. W. and Jones, P. H.:"Determination of the Interstitial-Water Content of Oiland Gas Sand by Laboratory Tests of Core Samples,"API Drilling and Production Practice (1944),pp.180­188.

4. Purcell, W. R.: "Capillary Pressures - TheirMeasurement Using Mercury and the Calculation ofPermeability Therefrom," Trans. AIME, vol. 186(1949), pp. 39-48.

5. Rose, Walter and Bruce, W. A.: "Evaluation of CapillaryCharacter in Petroleum Reservoir Rock," PetroleumTransactions, AIME, May 1949, pp. 127-142.

6. Burdine, N. T.: "Relative Permeability Calculations fromPore Size Distribution Data," Petroleum Transactions,AIME, vol.198, (1953), pp. 71-78.

7. Thomeer, J. H. M.: "Introduction of a Pore Geomtric;alFactor Defined by the Capillary Pressure Curve," JPT,(March 1960), pp. 73-77.

8. WardlOYl, N. C.: "Pore Geometry of Carbonate Roc;ksas Revealed by Pore Cast of Capillary Pressure,"AAPG Bulletin, vol. 50, No.2, (1976) pp. 245-257.

9. Swanson, B. F.: "A Simple Correlation BetweenPermeabilites Mercury Capillary Pressures," JPT,(December 1981), pp. 2498-2504.

10. Walls, J. D. and Amaefule, J. 0.: "Capillary Pressureand Permeability Relationships in Tight Gas Sands,"SPEIDOE 13879 Presented at the SPEIDOE 1985,Denver, CO, (May 19-22,1985.

11. Donaldson, Erie C., Thomas, Rex D., and Lorenz,Philip B.: 'Wettability Determination and Its Effect onRecovery Efficiency," Soc. Pet. Eng. J. (1969), pp. 13­20.

12. Brooks, R. H. and Corey, A. T.: "Properties of PorousMedia Affecting Fluid Flow," J. of Injection andDrainage Div. , Proc. of ASCE (1966), 92, No. 1R2, 61.

13. Hargoort, J.: "Oil Recovery by Gravity Drainage," Soc.Pet. Eng. J. (1980), pp. 139-150.

14. O'Meara Jr. D. J., and Lease, W.O.: "MultiphaseRelative Permeability Measurements Using anAutomated Centrifuge," SPE 12128 Presented at the

58th Annual Technical Conference of the SPE held inSan Franasco, CA, (October 5-8, 1983).

15. Amaefule, J. O. and Masuo, S.: ''The Use of CapillaryPressure Data for Rapid Evaluation of FormationDamage or Stimulation," SPE Prod. Engineering,March 1986, pp. 131-142.

16. O'Meara D. J. Jr., Hirasaki, G. J. and Rohan, J. A.:"Centrifuge Measurements of Capillary Pressure: Part1 -OutflOYI Boundary Condition" SPE 18296 Presentedat the 63rd Annual Technical Conference of the SPEheld in Houston, TX, (October 2-5, 1988).

17. Omoregie, Z. S.: "Factors Affecting the Equivalency ofDifferent Capillary Pressure MeasurementTechniques," SPE Formation Evaluation (March,1988),147-155.

18. Hoffman, R. N.: "A technique for the determination ofcapillary pressure curves using a constantlyac;c;elerated centrifuge," Soc. Pet. Eng. J., vol. 3, pp.227-235.

19. Luffel, D. L.: "Further discussion of paper published inSoc. Pet. Eng. J., 1963 (A technique for thedetermination of capillary pressure curves, by R. N.Hoffman)," Soc. Pet. Eng. J. vol. 4.(1964), pp. 191­194.

20. Rajan, R. R.: ''Theoretically Correct Analytic;al Solutionfor Calculating Capillary Pressure-Saturation fromCentrifuge Experiments," Paper J presented at the1986 SPWLA, June 9-13. Engineers held in LasVegas, NV, (September 22-25,1985).

21. Ruth, D. W. and Wong, S.: "Calculation of CapillaryPressure curves from Data Obtained by the CentrifugeMethod". Second Annual Technical Conference of theSCA, Houston, Texas, August 17-18,1988.

22. Siobod, R. L.,Chambers, A., and Prehn, W. L. Jr.:"Use of Centrifuge for Determining Connate Water,Residual Oil, and Capillary Pressure Curves of SmallCores," Trans., AIME (1951) vol. 192,127-134.

111

SAMPLE Klinkenberg Permeability, md Porosity, percentFORMATION 10 Confining Confining Confining Confining

Stress, 800, psi Stress,2000 psi Stress, 800, psi Stress,2000 psiT1 880 858 23.4 23.2

BereaT2 52.5 51.1 17.7 17.5

Confining Confining Confining ConfiningStress, 800, psi Stress,2100 psi Stress, 800, psi Stress,2100 psi

Delaware 35 2.54 2.40 15.9 15.6

104 9.89 9.36 18.1 17.8Confining Confining Confining Confining

Stress, 800, psi Stress,2800 psi Stress, 800, psi Stress,2800 psiBend Conglomerate 5A 4810 3570 20.0 19.1

13A 2120 1680 17.7 17.1

Table 1 PERMEABILITY AND POROSITY DATA

SAMPLE TEST Brine Saturation, percent pore spaceFORMATION 10 METHOD 1 I 2 I 4 I 8 I 15 I 35 I 60 I 100

Berea T1 HSC 46.9 21.9 15.7 11.6 9.2 6.0 4.2 3.7OBC 54.2 42.7 27.6 20.4 14.2 10.6 9.0 8.1

T2 HSC 100.0 84.7 55.1 39.9 32.4 26.0 20.7 16.6OBC 100.0 93.4 68.0 50.7 39.9 29.9 25.6 22.4

Delaware 35 HSC 100.0 100.0 95.6 71.9 51.5 36.5 31.3 28.5OBC 100.0 100.0 100.0 86.0 58.9 46.2 41.8 38.2

104 HSC 100.0 100.0 82.1 45.8 33.0 24.4 21.4 19.2OBC 100.0 100.0 93.3 59.2 44.9 33.3 27.5 23.4

Bend Conglomerate 5A PPC 35.9 30.0 25.6 23.0 21.4 16.4 * *HSC 40.9 30.4 25.4 21.1 18.5 14.7 12.6 11.4OBC 56.1 42.5 35.6 32.1 30.3 28.7 27.6 26.1

13A PPC 46.2 39.2 34.3 30.5 27.7 22.3 * *

HSC 40.5 33.7 30.2 26.4 24.3 20.2 17.2 15.2

OBC 69.6 62.5 58.7 54.6 47.9 40.5 34.5 30.8

PPC= Porous Plate Capillary Pressure * Maximum 35 psi (3 bar plate)HSC= High Speed Centrifuge (Endface Saturations)OBC= Overburden Centrifuge (Endface Saturations)

Table 2 SATURATIONS FOR CENTRIFUGE AND POROUS PLATE STUDY

SAMPLE TEST Average Brine saturation, percent pore space IFORMATION 10 METHOD 100 psi

Berea T1 HSC 7.3OBC 13.3

T2 HSC 27.8OBC 32.6

Delaware 35 HSC 39.5OBC 47.8

104 HSC 28.3

OBC 35.6

Bend Conglomerate SA HSC 15.9OBC 29.2

13A HSC 20.0OBC 39.8

HSC= High Speed CentrifugeOBC= Overburden Centrifuge

Table 3 AVERAGE SATURATIONS FOR CENTRIFUGE STUDY

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SAMPLE r @ % 50 Endface Saturation

10 Ambient Confined

r, microns r, microns

T1 20.76 14.61

T2 4.15 2.40

35 1.23 0.55

104 2.74 1.70

SA 24.65 14.61

13A 24.65 1.55

Table 4 MEDIAN PORE THROAT SIZE

Mean Standard Percent FrameworkSAMPLE Grain Size Deviation Cement Grains Matrix

10 (mm) (sorting) Modal % Modal % Modal %13A 0.91 0.82 9.2 80 0.8SA 0.9 0.47 7.2 71 1.635 0.06 0.02 21.2 54 1.6

T2 0.12 0.03 19.2 56 0.0

T1 0.18 0.05 11.6 53 0.0104 0.07 0.02 20.4 53 0.0

Table 5 TEXTURAL AND COMPOSITIONAL DATA

SAMPLE Saturation,%pore space @ 100 psi10 Ambient Confined Difference

13A 15.2 30.8 15.6SA 11.4 26.1 14.7

35 28.5 38.2 9.7

T2 16.6 22.4 5.8

T1 3.7 8.1 4.4104 19.2 23.4 4.2

Table 6 SATURATION DIFFERENCE

COREDRAINAGEPOSITION

Figure 1 CENTRIFUGE TEST AT HYDROSTATIC STRESS113

16X

90

20

o

80

70

10

!

iI

w

~w:E9(!)z8ozwm

SAMPLE5A 100 r-....,.--....,.---~r'"iiiii"'C:;-~~=-- ~=-:--::l

o 10 20 30 40 50 60 70 80 90 100

Fiqure 2 Brine Saturation. percent pore space

o OVERBURDEN• AMBIENT* POROUS PLATE100 -r---.....---4V------::==---==-~~__:__===_~

16X

oo

90

20

70

50

60

80

30

10

!

II

10 20 30 40 50 60 70 80 90 100

Fiqure 3 Brine SatLnlion. percent pore space

AI centrifuge saturations are calcUated end-face values

w~a::w:E9(!)zo(.)

ozwm

SAMPLE13A

114

SAMPLE T1 100 ,...-4~?--------=~

iJSa:wm

I

!I

90

80

70

60

50

30

20

10

o

50X

100 -r--------4~-e-----_'r""""!_=::I,......___-"":'lII"'"_""==

iJSa:wm

90

80

70

60

50

30

20

10

o 10 20 30 40 50 60 70 80 90 100

Fiqure 4 Brine Saturation, percent pore space

• AMBIENT 0 OVERBURDEN

50X

SAMPLET2 0o 10 20 30 40 50 60 70 80 90 100

Fiqure 5 Brine 8a1uration, percent pore space

All centrifuge saturations are calculated lind-face values

115

90

wa::~:swo

!

II

80

70

60

50

30

20

10

oo 10 20 30 40 50 60 70 80 90 100

Figure 6 Brine SatLration, percent pore spaceI

• AMBIENT 0 OVERBURDEN

100 r--lr----"iii~:;.=:~rn~ii~

10

SAMPLE 104 0o 10 20 30 40 50 60 70 80 90 100

Figure 7 Brine saturation, percent pore space

All centrifuge saturations are calculated end-face values

sox

30

20

50

60

80

90

70wa::~:swo

116

100

BEND CONGLOMERATESAMPLE 13A

• 0

• 0

t • 010

&LI..,

• AMBIENT • 0

o OVERBURDEN

• 0

e 01

1 10 100

Figure. 8 End-Face Brine Saturation, percent pore space

10

BEREASAMPLET2 e 0

eo

eo

~ 15 eoLL,..,

• AMBIENT e 0

o OVERBURDEN

eo

r0.1

1 10 100

Figure 9 End-Face Brine Saturation, percent pore space

117