10.1.1.72.1815

©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016

PRODUCING ULTRALOW INTERFACIAL

TENSION AT THE OIL/WATER

INTERFACE

T. Al-Sahhaf, A. Suttar Ahmed, and A. Elkamel*

Department of Chemical Engineering, KuwaitUniversity, P.O. Box 5969, Safat 13060, Kuwait

ABSTRACT

In view of the world-wide shortage of petroleum and the factthat a large amount of residual oil will remain in the reservoirafter the primary recovery and water flooding stages, theuse of Enhanced Oil Recovery (EOR) methods to recover asmuch as possible of this residual oil has become increasinglyimportant worldwide. The predominant and most promisingEOR technique is the micellar-polymer flooding processwhich uses a surface active agent (a surfactant) to decreaseinterfacial tension and hence allows oil to freely move from itsoriginal location through the porous media. The purpose ofthis paper is to present an experimental study of the factorsaffecting the equilibrium interfacial tension (IFT) at theoil/water interface. A large number of experiments wasconducted to study the variations of IFT as a function ofmany parameters including reservoir temperature, pressure,

773

DOI: 10.1081/LFT-120003712 1091-6466 (Print); 1532-2459 (Online)Copyright & 2002 by Marcel Dekker, Inc. www.dekker.com

PETROLEUM SCIENCE AND TECHNOLOGY

Vol. 20, Nos. 7 & 8, pp. 773–788, 2002

*Corresponding author. E-mail: [email protected]



surfactant concentration, and salinity. An Arabian heavycrude oil was used in the analysis along with three differentsynthetic surfactants and two formation waters. The pendentdrop technique enhanced by video imaging was employed formeasuring IFT. It was found that for the ranges of variablesconsidered in this study, IFT decreases with temperature andsalinity, increases with pressure, and decreases exponentiallywith surfactant concentration.

Key Words: Interfacial tension; Enhanced oil recovery;Pendent drop technique; Surfactant

INTRODUCTION

In almost all of the oil producing countries, it is necessary to maintainthe flow of oil at a substantial level for a sustainable growth of the economy.In the last century, oil exploration, drilling and dependency on oil and oilrelated products have revolutionized the oil industry. The recovery of thisvaluable commodity from oil reservoirs is essential for both the user andproducer nations. It is realized that sixty percent of the oil remainedentrapped in the porous rock of the formation after secondary recovery(Sharma and Shah, 1989 and Gregory, 1994). For extraction of this valuableresidual oil, associated gas lift, water or aqueous chemical solution floodingare the most efficient methods in practice. The tertiary oil recovery is mainlydependent on the properties of oil/aqueous/formation interfaces. Theseare capillary forces, contact angle, wettability, viscous forces and interfacialtension. These properties are represented by a dimensionless group called thecapillary number, NC, that is a measure of the mobilization of the occludedoil to enhance the oil recovery:

NC ¼�v

� cos �

� �ð1Þ

where � is the dynamic viscosity of the liquid, v is the velocity, � isthe contact angle and � is the interfacial tension (IFT) between the waterphase and the oil phase.

For better EOR efficiencies, the capillary number, NC, has to bemaximized by either increasing viscosity or reducing interfacial tension.Viscosity can be increased by flooding with chemical solutions of highapparent viscosity while interfacial tension is reduced by the injection ofa surfactant solution to the reservoir. The former option is dearer than

774 AL-SAHHAF, AHMED, AND ELKAMEL



the latter one due to the high cost involved in the pumping of polymersolutions.

Displacement by surfactant solutions is one of the important tertiaryrecovery processes by chemical solutions. The addition of surfactantdecreases the interfacial tension between crude oil and formation water,lowers the capillary forces, facilitates oil mobilization, and enhances oilrecovery. This process is known in the petroleum industry by severalnames. Hill et al. (1973), Larson and Hirasaki (1978), Shah andSchechter (1977) named the process as surfactant flooding. The term micel-lar flooding was used by Davis and Jones (1968), Gogarty (1976), Farouq Aliand Stahl (1972), Gupta and Trushenski (1978), Sayyouh et al. (1981), andTrushenski et al. (1974). Based on interfacial criteria, Foster (1973) namedthe process ‘‘low tension water-flooding’’. The term micro-emulsion flood-ing was introduced by Heally and Reed (1974, 1977). While Holm (1971)used the term soluble oil flooding.

The applications of surfactant in EOR have been studied since theincrease in demand of the commercial use of the crude oil. Bansal et al.(1977) investigated the interfacial behavior between aqueous and oil phases.They reported that the recovery of oil is mainly dependent on miscibility andmobility control of oil/water/rock interface. Interfacial tension is the majorcontributor in miscibility of oil as micro-emulsion and mobility from theformation rock. The lowering of IFT values results in the entrapped oilto move freely out of the rock matrix. Krumrine (1982) discussed thesurfactant use in sandstone formations. High concentrations of surfactantin the form of slug were tested either in low concentration of salt or with nosalt. Camilleri et al. (1987) have reported the enhancement of the phasebehavior by the addition of alcohol as a co-surfactant into the surfactantslug. They claimed that their pseudo-phase equilibrium model couldsatisfactorily predict the pseudo-phase compositions of pseudo-componentfor ternary or quaternary representations.

A surfactant solution is able to lower the interfacial tension betweenthe oil and the water phase and hence allows the entrapped oil to movefreely out of the reservoir or rock matrix. IFT measurements for differentconditions are therefore essential to evaluate the surfactant floodingtechnique as a viable EOR technique. One of the methods of measuringIFT is the pendent drop technique. This technique is an important practicaltechnique since it permits continuous study of interfacial phenomenawithout mechanical interference that occurs when other techniques areused. The technique involves the formation of a drop of oil on the tip ofa capillary tube, both immersed in the bulk fluid (aqueous phase). In appli-cations of the pendent drop technique, several methods such as the shapefactor method and the regression method have been developed by previous

PRODUCING ULTRALOW INTERFACIAL TENSION 775



investigators for extracting IFT information from the shape of pendentdrops. Interfacial tension was first studied using the pendent drop apparatusby Andrease et al. (1938). The technique was improved by Schoettle andJennings (1968) to enable the measurement of IFT at high pressures andhigh temperatures. Jennings (1969) was the first one to report data on theIFT of n-Decane/Water systems at temperatures of up to 176�C, and from1 to 817 atm. He also found that the effect of temperature was much greaterthan the effect of pressure.

A number of recent improvements to the pendent drop techniqueappeared recently. Doyle and Carrol (1989) introduced a syringe micro-meter head of increased capacity which allowed a wider range of IFTs tobe measured. The head is also capable of outputting in BCD form andallowed the technique to be made on-line. Satherley et al. (1990) useda video image process to extend the range of measurements using an inflec-tion plane method. Herd et al. (1992) described the method where a camerais used to display an image of the pendent drop on a monitor, which is thenprocessed by a frame digitizer board and computer software to determinethe IFT. Lin and Hwang (1994) showed that the technique is useful for theexperimental determination of ultralow dynamic interfacial tension. Theycomputed the IFT from a best-fit between the coordinates of a digitizeddrop profile and a theoretical curve obtained from the Laplace equation.Finally, Guo and Schechter (1997) developed a method for ultralow IFTdetermination on the basis of force balance on the lower half of a pendentdrop. They formulated a simple equation relating IFT, fluid densities, anddrop geometry.

A number of studies appeared in the past for measuring IFT of oilagainst water at reservoir temperatures and pressures. Firoozabadiand Ramey (1988), for instance, presented measurements and graphicalcorrelations for estimating the IFT of hydrocarbon liquids against water.Goebel and Lunkenheimer (1997) presented IFT experimental data for then-Alkane/Water system. Amin and Smith (1998) presented IFT measure-ments for three binary systems (methane–pentane, methane–heptane, andmethane–decane). The effect of pressure and temperature on IFT for thesesystems was studied. Badakhshan and Bakes (1990) studied the effect ofdifferent surfactants on IFT for a range of salt concentrations, temperatures,and surfactant concentrations. Three systems were studied: the n-Hexane/Water, Cycloexane/Water, and Toluene/Water systems. Cai et al. (1996)presented experimental data on IFT of ten hydrocarbon mixtures againstwater or brine. Al-Sahhaf et al. (2001) presented recently a study that estab-lished the variation of IFT of the n-Octane/Water system under a wide rangeof conditions of temperatures, pressures, salt, and surfactant concentrations.Three different surfactants were used: two cationic and one anionic.




Flock et al. (1986) used real crude oils to study the effect of temperature onthe interfacial tension. They carried out measurements of IFT versus tem-perature at a constant pressure.

The objective of the present study is to investigate the effect ofpressure, temperature, salinity, and surfactant concentration on IFT at theoil/water interface. A Kuwaiti crude oil is used in the analysis. Furthermore,three different surfactants were used and screened to select the surfactantthat most lowers the IFT. The IFT of the crude oil was also measured whenformation water is used along with different surfactant concentrations. In allmeasurements, the pendent drop technique enhanced by video imaging wasused for the accurate determination of IFT. The IFTs reported in this studyare obtained after all formed oil droplets reached a steady state andequilibrium was established between the oil phase and the aqueous phase.

EXPERIMENTAL WORK

Material and Equipment

For the aqueous phase, double distilled de-ionized water was obtainedfrom the Department of Chemical Engineering at Kuwait University. Twonormal hydrocarbons (n-Decane and n-Hexane) with a purity greaterthan 99% were obtained from Fluka Chemicals. These were used in orderto calibrate and check the operation of the equipment by comparingtheir IFTs against water with published results. A Kuwaiti crude oil witha specific gravity of 0.883 (at 60�F) and an API of 29 was obtained fromKuwait Oil Company (KOC). The crude oil was obtained fresh from wellRawdhatain RA-123T, was protected from the atmosphere, and stored in acarefully cleaned plastic-lined container. Two formationwaters thatwere usedin water flooding in KOC were also used in the analysis. The salt solutionswere prepared using distilled water. Three surfactants, Dodecyl BenzeneSulfonic Acid Sodium Salt, Sodium Dioctyl Sulfosuccinate (Alcopol O 70PG), and Hexadecyl Trimethyl Ammonium Bromide (Cetrimide) ofcommercial grade were purchased from Fluka, Aldrich, and SigmaChemicals Co., respectively.

The measurement of IFT needed a viewable chamber, observationequipment, and temperature and pressure control (Figure 1). A lightsource was required to illuminate the oil droplet in the glass windowedchamber. The Mitsubishi color video copy processor of ModelNo. CP 110U and Sony Video recorder MVR-5300 were used to save andprint the photograph of the bubbles. For more accuracy, a Polaroid Cameraof model No. Nikon UFX-DX Japan No. 613253 was also employed to




print the pictures of the bubbles. A heating jacket was used to increase theinternal temperature of the cell. A needle tip was screwed onto the top of aneedle holder, and this needle assembly was inserted beneath the cell. Thebottom of the needle holder was fastened to the lower double valveassembly.

The cell employed a sensitive metering valve with a vernier formaximum control of oil drop formation. Other valves served to isolatethe system during needle tip change-out, and to allow introduction of thedifferent fluids. The back pressure regulator plumbed to the top of the cellallowed flushing out through the top. A trinocular microscope was used toview the formation of the oil droplet, and to measure droplet dimensionsphotographically (by using either the Polaroid attachment or the videocamera system or both). The stainless steel needle tip and holder weresealed by Teflon gaskets.

For the formation of oil droplets, it was very important to comparea needle tip to the behavior of the oil/aqueous phase system under investi-gation. At the stage when the oil droplet reached equilibrium and was about

light source

drainage CCD

Camera

Monitor

V.C.R.

Function

Viewing

Cell

Water Pump Oil Pump

Figure 1. Experimental apparatus used for measuring IFT.




to detach, the IFT was measured at the required conditions of temperatureand pressure. Pressurizing the IFT cell needed an initial pump pressure, aliquid thermal expansion during heating, and a final pump pressureadjustment.

Procedure and Calculation Method

Due to the sensitive nature of IFT measurements, the Pendent Dropcell was thoroughly cleaned between each run. A procedure was developedwhereby the cell was successively flushed with chromic acid, hot water,acetone, and then air-dried to insure a contamination-free environment.The cell was also leveled on top of a vibration-free table that reduces theinference of constant low-frequency vibrations.

After the Pendant Drop cell was charged with bulk fluid, it waspressurized and heated to the working pressure and temperature. The oilphase was introduced through a heated line and forced through the needleinto the bulk fluid. The investigated temperatures and pressures ranged from25 to 110�C and 100 to 4500 psi, respectively. The drop parameters weremeasured from the drop dimension (Figure 2). The IFT was calculatedbased on the formula:

� ¼ 1=H��g½de�2

ð2Þ

where~�¼ density difference in g/cm3.de¼maximum diameter of the unmagnified drop in cm.g¼ gravitational constant at the point of measurement in cm/s2.1/H¼ shape factor based on the ratio of d(s)/d(e)¼ f(S).dn¼ the actual needle tip diameter in cm.do¼ the diameter of the needle after magnification in cm.

The magnification factor is determined by the ratio of dn/do where do isthe measured tip diameter as obtained from the photograph of the drop.The value of 1/H was obtained from the tables relating H and S asdetermined by Bartell and Niederhauser (1949) for the range of S of0.46–1.03, and by Stauffer (1965) for the extended range to values of Sdown to 0.30. The experimental procedure was checked by taking eachexperiment at least thrice. In addition, to further check our measurementprocedure for IFT, we made two extra runs, one for n-Decane and one forn-Hexane. Our value of 52.431 dyne/cm at 25�C for the n-Decane/Watersystem was in excellent agreement with the value of 51.79 dyne/cm at 25�C




reported by Motomura (1983) and our value of 50.68 dyne/cm at 25�C forthe n-Hexane/Water system was also in excellent agreement with the valueof 51.10 reported in the CRC Handbook of Chemistry and Physics (1979).We concluded from these results that our procedure for obtaining pureliquids and cleaning the apparatus provides interfaces practically free ofcontamination.

EXPERIMENTAL RESULTS

The interfacial tension between heavy crude oil and injection waterunder reservoir conditions plays an important role in oil recovery studies.It is well known that temperature is the most significant factor affectingIFT. The addition of surfactants decreases IFT further, thus improvingthe efficiency of oil recovery. The dominant mechanism is the reduction ofIFT at the oil/water interface resulting in the mobilization of oil by in-situemulsification. The purpose of this section is to study the effect of surfactantaddition and temperature on the IFT of a Kuwaiti crude oil. In addition, theeffect of salinity of the injected water and reservoir pressures is also inves-tigated. Two formation waters that are employed in water flooding werealso considered. Various experiments were conducted varying the different

de de

ds

dn

Figure 2. Oil droplet dimensions for the calculation of IFT.




factors mentioned above. The quantification of the relationship of IFT withthese factors is important in the assessment of the application of enhancedoil recovery using surfactants. Three different surfactants were considered:

1) Sodium Dodecyl Benzene Sulfonic Acid Sodium Salt. The mole-cular weight of this surfactant is 348.48 g and the chemicalformula is:

CH3 � ðCH2Þ11C6H4SO3Na � CH3 � C11H22 � C6H4SO3Na

�C12H25 � C6H5 �HSO3Na

2) Hexadecyl Trimethyl Ammonium Bromide. The molecular weightof this surfactant is 364.46 g and its formula is:

CH3ðCH2Þ15NðCH3Þ3BrCH3 � C15H30 �NðCH3Þ3Br

�C16H33 �NðCH3Þ3Br

3) Dioctyl Sulfosuccinate Sodium Salt. The molecular weight of thissurfactant is 444.55 g and its formula is:

CH3ðCH3Þ3 � CHðC2H5ÞCH2O2 � C � CH2 � CHðSO3NaÞCO2

� CH2ðC2H5Þ:ðCH2Þ3 � CH3¼C19H37SO7Na

A number of experiments were first carried out to screen the various surfac-tants. Figure 3 shows the variation of IFT with pressure at a temperature of65�C for the three surfactants. Surfactant (1) has the most effect on loweringIFT. The effectiveness of this surfactant was also checked at other tempera-tures and salinities. It was always lowering the IFT the most as compared to

Figure 3. Variation of IFT with the various kinds of surfactants at 65�C and 1 wt%surfactant concentration.




the other two surfactants. Therefore, only this surfactant was considered forfurther investigation.

In the initial stages of the experiments, only pure water was used. Nosurfactant was added and no salt, either. Figure 4 shows the variation ofIFT as a function of both temperature and pressure. The figure shows thatboth temperature and pressure affects IFT. The effect of temperature ismore pronounced.

The effect of surfactant concentration and salt is shown in Figure 5. Ascan be seen, the addition of surfactant has a great effect on lowering the

Figure 5. Variation of IFT with the concentration of surfactant (1) at 500 psi,50�C, and three different NaCl concentrations.

Figure 4. Variation of IFT of crude oil with pressure and temperature.




IFT. The lowering of IFT by the surfactant is almost exponential. NaCl alsolowers IFT. The effect of temperature and pressure on IFT in the presenceof NaCl is shown in Figure 6. The same behavior is exhibited as in Figure 4.The effect of temperature and pressure on IFT in the presence of surfactantand NaCl is shown in Figure 7. Again, the same effect is observed. The IFT’sin this figure are, however, much lower due to the presence of the surfactant.

The IFTs of the crude oil versus two different formation waterswere also investigated. Figure 8 shows the variation of IFT for the firstformation water. This water has a density of 1.1663 g/cm3 at 25�C and apH of 3.85. Figure 9 shows the variation of IFT for the second formation

Figure 6. Effect of temperature and pressure on IFT in the presence of 1wt%NaCl.

Figure 7. Variation of IFT with temperature and pressure in the presence of 1wt%NaCl and 1wt% surfactant (1).




water. This water has a density of 1.0016 g/cm3 and a pH of 7.19. Theconditions of the 1st formation water are more favorable for loweringIFT (Figure 10).

CONCLUSION

The mechanism of tertiary oil recovery depends heavily on theproperties of the crude oil/aqueous/rock interfaces. In the present study,

Figure 8. Variation of IFT as a function of temperature and pressure for the firstformation water.

Figure 9. Variation of IFT as a function of temperature and pressure for thesecond formation water.




an attempt was made in order to quantify the IFT at the crude oil/aqueousinterface. The measurements of IFT were conducted using the PendentDrop apparatus enhanced by video imaging. Four different variableswere investigated in this study: temperature, pressure, salinity, and surfac-tant concentration. In addition, three different surfactants were screened inorder to find out which lowers IFT at the oil/water interface the most.These surfactants were: Sodium Dodecyl Benzene Sulfonic Acid SodiumSalt (1), Hexadecyl Trimethyl Ammonium Bromide (2), and DioctylSulfosuccinate Sodium Salt (3). It was found that surfactant (1) hasthe greatest effect on reducing IFT. This result was the same at differenttemperatures, pressures, and salinities. Two formation waters used inwater flooding were also screened in order to determine which waterfavors the lowering of IFT. For the ranges of the experiments considered

Figure 10. Comparison for the variation of IFT as a function of pressure for thetwo formation waters and at three different temperatures.




in this study and with the heavy Kuwaiti crude oil, IFT was foundto decrease with increasing temperatures and salinities, increase withincreasing pressures, and exponentially decrease with increasing surfactantconcentrations.

ACKNOWLEDGMENT

The authors would like to thank the research administration unit at

Kuwait University for sponsoring this research under grant EC072. We

would also like to thank Prof. El-Gibaly for many helpful discussions at

the beginning of this work.

REFERENCES

Al-Sahhaf, T.; Ahmed, A.S.; Elkamel, A.; Khan, A.R. The Influence ofTemperature, Pressure, Salinity, and Surfactant Concentration on theInterfacial Tension of the n-Octane–Water System, 2001, Submitted forpublication.

Amin, R.; Smith, T. Interfacial Tension and Spreading Coefficient UnderReservoir Conditions. Fluid Phase Equilibria 1998, 142, 231–241.

Andreas, J.M.; Hauser, E.A.; Tucker, W.B. Journal of Physical Chemistry1938, 42, 1001.

Badakhshan, A.; Bakes, P. The Influence of Temperature and SurfactantConcentration on Interfacial Tension of Saline Water and HydrocarbonSystem in Relation to Enhanced Oil Recovery by Chemical Flooding, SPEpaper 20290, 1990.

Bansal, V.K.; Shah, D.O.; Chan, K.S. The Importance of Interfacial Chargewith Interfacial Tension in Secondary and Tertiary Oil RecoveryProcesses. Proceeding of AIChE 83rd National Meeting, March 98,1977.

Bartell, E.F.; Niederhauser, D.O. Film Forming Constituents of CrudePetroleum Oils, Fundamental Research on Occurrence and Recoveryof Petroleum, API 1949, 1946–47.

Cai, B.Y.; Yang, J.T.; Guo, T.M. Interfacial Tension of HydrocarbonþWater/Brine System under High Pressure. J. Chem. Eng. Data 1996,41, 493–496.

Craigm, F.F. Jr. The Reservoir Engineering Aspects of Water-Flooding. SPEMonograph Series, SPE Dalls, 1971.




Camilleri, D.; Fil, A.; Pope, G.A.; Sepehrnoori, K. Improvements inPhysical Property Models Used in Micellar/Polymer Flooding, SPEReser. Eng. 1987, 433–440.

CRC Handbook of Chemistry and Physics, 59th Ed.; Weast, R.C., Ed.; CRCPress: Boca Raton, FL, Sec. F, 1979; 45–47.

Davis, J.A. Jr.; Jones, S.C. Displacement Mechanism of Micellar Solutions,J. Pet. Tech. 1968 December.

Doyle, P.J.; Carroll, B.J. An Improved and Semi-Automated Version of theDrop Volume Technique for Interfacial Tension Measurement, J. Phys.E: Sci. Instrum. 1989, 22, 431–433.

Farouq Ali, S.M.; Stahl, C.D. Tertiary Recovery of the Bradford Crude Oilby Micellar Solutions from Linear and Two-Dimensional Porous Media,Paper SPE 3994. Presented at the 47th Annual Fall Meeting, Texas,1972.

Firoozabadi, A.; Ramey, H.J. Surface Tension of Water–HydrocarbonSystems at Reservoir Conditions. Reservoir Engineering 1988, 27(3),41–48.

Flock, D.L.; Gibeau, J.P. The Effect of Temperature on the InterfacialTension of Heavy Crude Oils Using the Pendent Drop Apparatus,The Journal of Canadian Petroleum Technology 1986, March–April,72–77, Montreal.

Foster, W.R. Low-Tension Water Flooding Process, J. Pet. Tech. 1973,25, 205.

Goebel, A.; Lunkenheimer, K. Interfacial Tension of the water/n-alkaneInterface. Langmuir 1997, 13, 369–372.

Gogarty, W.B. Status of Surfactant of Micellar Floods. J. Pet. Tech. 1976,January, 93–102.

Gregory, A.T. DTI’s Improved Oil Recovery Strategy. Trans. Ichem. E.1994, 72(Part A) 137–143.

Guo, B.; Schechter. A Simple and Accurate Method for Determining Low IFTfrom Pendant Drop Measurements, Paper SPE 37216, Presented at theInternational Symposium on Oilfield Chemistry, Houston, Texas, 18–21February, 1997, 59–70.

Gupta, S.P.; Trushenski, S.P. Micellar Flooding the Design of the PolymerMobility Buffer Bank. Soc. Pet. Eng. J. 1978, February, 5–12.

Healy, R.N.; Read, R.L. Physicochemical Aspects of MicroemulsionFlooding, Soc. Pet. Eng. J. 1974, 14, 491–501.

Healy, R.N.; Reed, R.L. Immiscible Microemulsion Flooding, Soc. Pet.Eng. J. April, 1977, 129–139.

Herd, M.D.; Lassahn, G.D.; Thomas, C.P.; Bala, G.A.; Eastman, S.L.Interfacial Tensions of Microbial Surfactants Determined by Real-TimeVideo Imaging of Pendant Drops, SPE/DOE paper 24206, Presented at




the Eighth Symposium on Enhanced Oil Recovery, Tulsa, Oklahoma,April 22–24, 1992, 513–519.

Hill, H.J.; Reisberg, H.; Stegemeier, G.L. Aqueous Surfactant System forOil Recovery, J. Pet. Tech. 1973, 25, 186.

Holm, L.W. Use of Soluble Oil for Oil Recovery. J. Pet. Tech. December,1971, 1475–1483.

Jennings, H.Y. The Effect of Temperature and Pressure on the IFT ofBenzene–Water and n-Decane–Water. Journal of Colloid andInterface Science 1969, 24(3), 323–329.

Krumrine, P.H. The Effect of Alkaline Additives on IFT, SurfactamntAdsorption, and Recovery Efficiency. Soc. Pet. Eng. J. August, 1982.

Larson, R.G.; Hirasaki, G. Analysis of Physical Mechanisms in SurfactantFlooding, Soc. Pet. Eng. J. 1978, February.

Lin, S.Y.; Hwang, F.H. Measurement of Low Interfacial Tension byPendant Drop Digitization. Langmuir 1994, 10, 4703–4709.

Motomura, K. Journal of Colloid and Interfacial Science 1983, 93(1),264–269.

Satherley, J.; Girault, H.H.J.; Schiifin, D.J. The Measurement of UltralowInterfacial Tension by Video Digital Techniques,’’ Journal of Colloidand Interface Science 1990, 136(2).

Shah, D.O.; Schechter, R.S. Improved Oil Recovery by Surfactant andPolymer Flooding. Academic Press Inc., 1977.

Sayyouh, M.H.; Farouq Ali, S.M.; Stahl, C.D. Rate Effect in the TertiaryMicellar Flooding of the Bradford Crude Oil, Soc. Pet. Eng. J. August,1981, 469–479.

Schoettle, V.; Jennings, H.Y. High-Temperature Visual Cell for IFTMeasurements, The Review of Scientific Instruments, 1968, 24(3).

Sharma, M.K.; Shah, D.O. Use of Surfactants in Oil Recovery, In EnhancedOil Recovery II Processes and Operations, Erle, C. Donaldson, GeorgeV. Chilingarian, The Fu Yen, Eds.; Elsevier: New York, 1989; 253–315.

Stauffer, C.E. The Measurement of Surface Tension by the Pendent DropTechnique. J. Phys. Chem. 1965, 69, 1933.

Trushenski, S.P.; Dauben, D.L.; Parrish, D.R. Micellar Flooding–FluidPropagation, Interaction, and Mobility. Soc. Pet. Eng. J. 1974,December.

Received July 21, 2001Accepted October 1, 2001


10.1.1.72.1815

Documents

express written permission

bradford crude oil

kuwaiti crude oil

pendent drop technique

enhanced oil recovery

pendent drop apparatus

rst formation water

pendent drop