A Study of Caustic Solution-Crude Oil Interfacial Tensions

1975 ◽  
Vol 15 (03) ◽  
pp. 197-202 ◽  
Author(s):  
Harley Y. Jenning
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Sodium Hydroxide ◽  
Surface Activity ◽  
Acid Number ◽  
Caustic Solution ◽  
Crude Oils ◽  
Interfacial Tensions ◽  
Drop Method ◽  
Pendent Drop

Abstract This paper presents the results of a study of caustic solution-crude oil interfacial tension measurements on 164 crude oils from 78 fields. Of these crude oils 131 showed marked surface activity against caustic solutions. Surface activity of crude oil against caustic solution correlates with the acid number, gravity, and viscosity. Almost all crude oils with gravities of 20 degrees API or lower produced a caustic solution-crude oil interfacial produced a caustic solution-crude oil interfacial tension less than 0.01 dyne/cm. Of the interfacially active samples, 90 percent reached maximum measurable surface activity at a caustic concentration of close to 0.1 percent by weight. The dissolved solids content of the water bas a marked influence on the surface activity. Sodium chloride in solution reduces the caustic concentration required to give maximum surface activity. Conversely, calcium chloride in solution suppresses surface activity. Introduction The oil-production technology literature contains a number of papers that indicate that the addition of sodium hydroxide to the flood water beneficially affects oil recovery. Although the proposed recovery mechanisms differ in detail, a variable common to almost all is the interfacial tension between caustic solutions and crude oil. A study of the factors influencing caustic solution-crude oil interfacial tensions is fundamental to an understanding of the proposed mechanisms and their optimum utilization. proposed mechanisms and their optimum utilization. We have obtained interfacial tensions against caustic solutions of 164 crudes. These crudes come from all major oil-producing areas in the free world. In addition to determining the correlation of interfacial tension with crude oil properties of acid number, gravity, and viscosity, we have also determined the effect of certain dissolved solids in the water. We define acid number as the number of milligrams of potassium hydroxide required to neutralize the acid in one gram of sample. The interfacial tension data were obtained by the pendent-drop method. pendent-drop method. EXPERIMENTAL PROCEDURE The caustic solutions used in this study were prepared by adding reagent-grade sodium hydroxide prepared by adding reagent-grade sodium hydroxide to laboratory distilled water. Our standard solutions were made from a 50 percent by weight reagent-grade sodium hydroxide solution. For convenience in relating our laboratory data to possible field application, the data were recorded and plotted in terms of weight percent sodium hydroxide. The pH of the caustic solutions was determined experimentally using a Coming expanded-scale pH meter; and the densities of the caustic solutions were measured experimentally using a Chainomatic Westphal balance. CRUDE OILS The crude oils were protected from the atmosphere and were collected in carefully cleaned glass or, when practicable, in plastic-lined containers. The crude oil samples were free of chemical additives, such as emulsion breakers and corrosion inhibitors. If the oil contained suspended solid material it was dehydrated and filtered. The densities were determined by the Westphal balance; and the viscosities were determined as a function of temperature using a glass capillary viscometer. APPARATUS AND EXPERIMENTAL PROCEDURE The interfacial tension measurements described in this study were made by the pendent-drop method. The pendent-drop method is based on the formation of a drop of liquid on a tip, the drop being slightly smaller than that which will spontaneously detach itself from the tip. The profile of this drop is magnified by projection and can be recorded on a photosensitive emulsion. The interfacial tension is photosensitive emulsion. The interfacial tension is calculated from the dimensions of the drop profile, a knowledge of be densities of the liquid forming. the drop, and the bulk phase surrounding the drop. All interfacial tensions described in this paper were recorded at a temperature of 74 degrees F and at an interface age of 10 seconds. Most systems were studied as a function of temperature; but temperature was found to be a second-order effect, so we selected 74 degrees F in order that all correlations would be at constant temperature. We selected 10 seconds because a study of the time variable showed that most of the decay of interfacial tension with time in these systems had occurred by the end of 10 seconds. SPEJ P. 197

The Effect of Temperature and Pressure on the Interfacial Tension of Water Against Methane-Normal Decane Mixtures

1971 ◽  
Vol 11 (02) ◽  
pp. 171-175 ◽  
Author(s):  
Harley Y. Jennings ◽  
George H. Newman
Keyword(s):  
Stainless Steel ◽  
Interfacial Tension ◽  
Water System ◽  
Visual Cell ◽  
Density Data ◽  
Interfacial Tensions ◽  
Drop Method ◽  
Temperature And Pressure ◽  
Live Oil ◽  
Pendent Drop

Abstract The interfacial tension of water against mixtures of methane and normal decane bas been measured in the interval 74 to 350 degrees F and 14.7 to 12,000 psia. These measurements show the range of interfacial-tension values obtained with water against an ideal "live-oil" system under reservoir conditions of temperature and pressure. The interfacial-tension data were obtained by the pendent drop method. The density data used for pendent drop method. The density data used for the pendent drop calculations were based on visual cell pressure volume measurements of the mutually saturated phases. Seven systems covering the methane-decane composition range from 100 percent decane to 100 percent methane were studied at three temperatures and 11 pressure intervals in the single-phase, hydrocarbon region. A minimum in the interfacial-tension vs methane-decane composition curve was observed. The minimum occurred at about the same composition in each isotherm, namely, with a mixture containing nearly equal weights of methane and decane. Both temperature and pressure affected the interfacial tension. For some compositions at constant pressure the interfacial tension increased with increased temperature. Introduction Although crude oil usually occurs in the formation saturated to some degree with methane, interfacial-tension data for methane-oil mixtures against water have not been published. These data are fundamental to an understanding of the role of interfacial forces in oil recovery and provide a basis for interpreting the interfacial tensions against water obtained with "live" crude-oil systems. We obtained interfacial tensions against water for an ideal "live-oil" composed of mixtures of methane and normal decane. Portions of this three-component (water, methane, normal decane) system have been studied and reported and these data serve as limits for our results. Hough et al. presented data for the methane-water system at presented data for the methane-water system at temperatures to 280 degrees F and pressures to 15,000 psia. Stegemeier studied the two-phase methane-decane system to 183 degrees F and 5,100 psia, and Jennings published results for the normal psia, and Jennings published results for the normal decane-water system to 350 degrees F and 12,000 psia. In this study we have obtained data for water-oil interfacial tension as a function of temperature to 350 degrees F. and pressure to 12,000 psia, using a series of live oils of known composition. The interfacial-tension data were obtained by the pendent drop method. EXPERIMENTAL MATERIALS Laboratory distilled water was redistilled into a steam-cleaned pyrex receiver connected to the atmosphere through an ascarite tower. The hydrocarbons used in this study were pure-grade normal decane and instrument-grade methane, both obtained from the Phillips Petroleum Co. The decane was further purified by fractional chromatography. APPARATUS The interfacial-tension measurements were made by the pendent drop method utilizing an apparatus designed to permit measurement of interfacial-tension values as low as 0.001 dynes/cm under high temperature and pressure. A novel feature of this apparatus is a pendent drop tip-holding turret designed to permit five tips to be rotated into position under operating conditions. The visual cell containing the turret is made of stainless steel, 4.5 in. in diameter and 7.5 in. long. The windows are glass discs 1.5 in. in diameter and 0.75 in. thick. All valves and connecting lines are of stainless steel and teflon seals are used throughout the apparatus. SPEJ P. 171

Modeling Crude Oils for Low Interfacial Tension

1976 ◽  
Vol 16 (06) ◽  
pp. 351-357 ◽  
Author(s):  
J.L. Cayias ◽  
R.S. Schechter ◽  
W.H. Wade
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Homologous Series ◽  
Carbon Number ◽  
Side Chain ◽  
Crude Oils ◽  
Alkyl Side Chain ◽  
Hydrocarbon Mixtures ◽  
Interfacial Tensions ◽  
Hydrocarbon Oil

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Using the correlation between interfacial-tension behavior for three homologous series of hydrocarbons and a simple, mole-fraction averaging procedure, it was found possible to predict interracial tensions for complex hydrocarbon oil phases/aqueous surfactant Phases. This leads to an extension of the equivalent alkane carbon-number (EACN) concept to a mixed hydrocarbon oil phase. The EACN for eight crude oils was determined and it was found that the interfacial tension of crudes can be best modeled by alkanes in the range of hexane to nonane. Introduction Previous publications, have demonstrated that low interfacial tensions can be attained with pure hydrocarbons as the oil phase. The aqueous phase contained surfactants that were proposed as candidates for tertiary oil recovery of crude oils, namely petroleum sulfonates and alkyl xylene sulfonates. These observations demonstrate that complex hydrocarbon mixtures are not a necessary requirement for low tensions and, as can be attested by any worker in the field, are certainly not a sufficient requirement for attaining low tensions. The question is, then, how can tensions for complex hydrocarbon mixtures (crude oils) be modeled given the tension of their components? Systematic trends in the tension have been observed for various hydrocarbon homologous series. It was found, for example, that an alkyl benzene gave the same interfacial tension as an alkane having the same number of carbon atoms as the alkyl side chain. The alkyl side chain is therefore the only contributor to the tension. Likewise, it was found that a cyclohexyl ring was approximately equivalent to four carbons. The hydrocarbon giving minimal tension can be varied by changing either the salinity or the surfactant concentration, but the above-mentioned scaling rules were found to apply. These observations have resulted in the concept of an equivalent alkane carbon number (EACN) for binary mixtures of alkanes, alkyl benzenes, and alkyl cyclohexanes. Hydrocarbon behavior was found to be additive and mole-fraction weighted by the simple relationship, (1) where the Ci are EACN values for the individual components, the Xi are mole fractions, and Cavg is the EACN for the mixture. For example, an equimolar mixture of butylcyclohexane (C1 = 4 for butyl groups + 4 for cyclohexyl = 8, X1 = 0.5) and propylbenzene (C2 = 3 for the propyl group + 0 for propylbenzene (C2 = 3 for the propyl group + 0 for benzene, X2 = 0.5) has a Cavg of 5.5. This mixture then would be predicted to yield a minimum interfacial tension against a surfactant solution that gives low tensions against pure alkanes intermediate between pentane and hexane. Eq. 1 has been verified for a wide variety of binary mixtures. Crude-oil behavior could be predicted by expanding Eq. 1 to the general form, (2) where the running index i extends over all the crude oil components. Of course, this cannot be accomplished in practice since all the components of a specific crude oil have never been identified. However, if Eq. 2 applies to complex but known-composition hydrocarbon mixtures, then applicability to crude oils can be inferred. Tests verifying Eq. 2 are reported in this paper. Eq. 2, in a variety of situations, requires that effects resulting from alkane isomerization be investigated. In addition, the role of sulfur compounds needs to be assessed. These studies also are reported. Finally, two different experimental techniques are used to validate the EACN concept as applied to crude oils, and values for eight samples are reported. EXPERIMENTAL PROCEDURE All interfacial tensions were measured without pre-equilibration at 27 degrees C using the spinning drop pre-equilibration at 27 degrees C using the spinning drop technique. Five sodium sulfonate surfactants were used: Witco TRS 10-80, Shell Martinez 380 and Martinez 470, and Exxon Chemical Dodecyl and Pentadecyl Xylene sulfonates. Pentadecyl Xylene sulfonates. SPEJ P. 351

Smackover Nacatoch Crude Oil Separation of Surfactant Precursors and Their Effect on the Crude

1981 ◽  
Vol 21 (04) ◽  
pp. 493-499 ◽  
Author(s):  
J.H. Runnels ◽  
C.J. Engel
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Sodium Hydroxide ◽  
Aqueous Phase ◽  
Oil Recovery ◽  
Crude Oils ◽  
Gel Chromatography ◽  
Active Materials ◽  
Tertiary Oil Recovery ◽  
Surface Active

Abstract An procedure is given for separating surfactant precursors that occur in some crude oils. The effect of the precursors on the properties of the oils are described also. The separations were made by silica gel chromatography on crude oil from which the asphaltenes had been removed. The effect of the precursors on the properties of the crude was evaluated by blending the surfactant precursors into the original oil, a modified oil, or a hydrocarbon solvent such as benzene. Precursors activated and converted to surface active materials by a strong base such as sodium hydroxide are effective in reducing the interfacial tension between the oil and aqueous phase. Occurrence of precursors in crude oils is essential for improved oil recovery by the causticflood process. The procedure for separating the precursors should provide a viable means for evaluating the applicability of a causticflood tertiary oil recovery process to a particular crude or reservoir. Introduction Tertiary oil recovery by the causticflood process is inherently dependent on naturally occurring surfactant precursors in the crude. The surfactant precursors react with the caustic (base) in the floodwater to form surface active compounds that reduce the interfacial tension between the crude and aqueous phase, alter the wettability of the mineral surfaces, or reduce rigid film formation at the crude/aqueous interface. In laboratory oil-recovery tests, these mechanisms stimulate oil production characterized by increased production at caustic breakthrough and a high oil/water ratio after breakthrough. An early effort to identify the surfactant precursors in a Rio Bravo (CA) crude concluded that the surfactant precursors were related closely to the asphaltene and resin fractions of the crude. Subsequent studies using an Eichlingen Niedersachen (West German) crude and a Ventura (CA) crude concluded that the surfactant precursors were acids and phenols, respectively. The extensive work of Seifert established that the surfactant precursors of a Ventura crude were carboxylic acids and that the phenolic components of the crude were interfacially inactive. The purpose of our study was to develop a simple and practical method of separating surfactant precursors from crude oil and to evaluate their effect on the interfacial tension, acid number, and other properties of the crude. The separation technique was developed using Smackover Nacatoch crude and the surfactant precursors evaluated were obtained from the same crude. Description of Smackover Nacatoch Crude The Smackover reservoir is located in southern Arkansas, and the Nacatoch pay zone is the shallowest of five pay zones. The crude has an API gravity of 21 degrees, a viscosity of 160 cp at room temperature, and is produced from an unconsolidated sand formation about 2,000 ft deep. Preliminary studies showed that the interfacial tension between the crude and an aqueous phase was reduced from about 12 to 0.02 dyne/cm when the pH of the aqueous phase was increased from 7.0 to 12.5 with sodium hydroxide. The significant reduction in interfacial tension at higher pH's indicated that the crude contained a relatively high concentration of surfactant precursors that were converted to surface active materials by sodium hydroxide. SPEJ P. 493^

Physical Characteristics of Natural Films Formed at Crude Oil-Water Interfaces

1966 ◽  
Vol 6 (02) ◽  
pp. 153-165 ◽  
Author(s):  
O.K. Kimbler ◽  
R.L. Reed ◽  
I.H. Silberberg
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Oil Recovery ◽  
Interfacial Area ◽  
Physical Characteristics ◽  
Petroleum Production ◽  
Drop Method ◽  
Oil Water ◽  
Interfacial Films ◽  
Pendent Drop

Abstract Interfacial films have frequently been observed at interfaces between certain crude oils and water. Several investigators have postulated that the presence of these films should influence the efficiency of oil recovery in water drive or waterflood operations. They may also influence the stability of emulsions which are sometimes a problem in petroleum production, and may be a factor in the formation of paraffin deposits in oil well tubing and flow lines. This paper presents a technique with which a modified Langmuir film balance may be used to study the compressibility and collapse pressure of these natural interfacial films. Experimental data are presented for several crude oil-water systems. Data developed are used to infer the phase state of the film as a function of such variables as rate of reduction of interfacial area, ionic composition of the subtrate and pH of the subtrate. A film of known physical characteristics is shown to have a significant effect on oil recovery from an unconsolidated sand pack. Possible applications of these results to petroleum production are discussed. INTRODUCTION The use of water to displace petroleum from reservoir rocks is of major importance both as a primary and a secondary recovery process. As water invades the rock, oil is completely displaced from some pores and left as a discontinuous phase in other pores. The manner in which water moves from pore to pore is strongly influenced by capillary forces. In view of the complexity of reservoir fluid systems, there can be little doubt that complicated interactions take place at both the liquid-solid and oil-water interfaces. One of the more interesting, and least understood, of the phenomena which take place at the oil-water interface is the formation of interfacial films. These films are believed to result from the adsorption of high molecular weight polar molecules at the interface.1,2 Presence of such molecules may cause a striking alteration in interfacial tension. When the oil-water interfacial area of certain crudes is rapidly reduced, a thin region (film) about the interface assumes the appearance of a solid membrane, and striations, wrinkles and gross distortions may occur. If such a film is solid, it should greatly alter the interfacial tension normally assumed to exist between the oil and water phases. If the membrane is continuous, a solid phase would separate the oil and water. Interfacial films between crude oil and water were observed in 1949 by Bartell and Niederhauser3 who commented upon the apparent rigidity of the films and their possible importance in the petroleum industry. Morrell and Egloff4 had earlier attributed the extreme stability of emulsions of sea water in fuel oil to very stable asphaltic films. Numerous investigators have observed rigid films in the course of crude oil-water interfacial tension determinations by the pendent drop method. Several investigators5,6,2 have separated interfacially active materials from crudes and attempted to characterize them chemically. Reisberg and Doscher,2 using Ventura crude, showed the interfacial tension against water (as measured by the pendent drop method) to be affected by aging, contraction and expansion of the interface, and the pH of the water. These investigators attributed the adhesion of oil to a water-wetted surface and the distortions of flow paths in glass capillaries to the presence of rigid films. Dodd7 has studied the interfacial viscosity of adsorbed films and found them to be non-Newtonian in behavior. Craighead and Harvey8 reported a series of displacements in tubes packed with 60 mesh glass beads. They interpreted the results as indicating an effect of stearic acid films on waterflood recovery and imply that natural films may produce similar results.

Low Interfacial Tensions Involving Mixtures of Surfactants

1977 ◽  
Vol 17 (02) ◽  
pp. 122-128 ◽  
Author(s):  
W.H. Wade ◽  
J.C. Morgan ◽  
J.K. Jacobson ◽  
R.S. Schechter
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Surfactant Concentration ◽  
Electrolyte Concentration ◽  
Hydrocarbon Mixture ◽  
Surfactant Mixtures ◽  
Interfacial Tensions ◽  
System Variables ◽  
Low Tension ◽  
Scaling Rule

Abstract The interfacial tension of surfactant mixtures with hydrocarbons obeys a simple scaling rule. Many apparently inert surfactants give low tensions when in mixtures; the scaling rule still applies to these mixtures. The influence of surfactant structure and molecular weight on low-tension behavior is examined, and the application of these results to the optimization of surfactant flooding systems is discussed. Introduction It has been shown that the interfacial-tension behavior of a given crude oil with a surfactant solution of the sulfonate type may be modeled by replacing the crude oil with one particular alkane. The number of carbon atoms in the alkane is referred to as the equivalent alkane carbon number (EACN) of the crude oil, and this EACN is independent of the surfactant used (at fixed standard conditions). This equivalency of a crude oil and an alkane is a result of the simple averaging behavior of hydrocarbons when mixed. Any hydrocarbon may be assigned an EACN value. For instance, when homologous series of alkyl benzenes and alkanes are run against the petroleum sulfonate TRS 10-80 at 2 gm/liter of surfactant with 10 gm/liter NaCl present, heptyl benzene and heptane, respectively, give minimum interfacial tensions, a. The EACN of heptyl benzene is 7, since it is equivalent to heptane. A simple averaging rule will give the EACN of a hydrocarbon mixture : (1) where x is the mole fraction of the ith component. Thus, an equimolar mixture of undecane (EACN 11) and heptyl benzene (EACN 7) has an EACN of 9. If a surfactant gives a low (minimum) sigma against nonane (EACN 9), it will also give a low sigma against the above mixture. Eq. 1 implies that a crude oil, which is a multicomponent hydrocarbon mixture, may be assigned an EACN. This has been verified experimentally. For example, Big Muddy field crude oil has an EACN of 8.5. Therefore, any surfactant phase giving a minimum tension against an equimolar mixture of octane and nonane gives a low tension against Big Muddy crude. All crude oils rested to date have EACN's ranging from 6 to 9. For a given surfactant, the alkane of minimum tension (min) may be affected by the electrolyte concentration or type, the temperature, the surfactant concentration, or the presence of a cosurfactant. These system variables may be adjusted until the nmin for a surfactant matches exactly the EACN of a crude oil. For any particular surfactant, many different combinations of variables will give the same n min value; therefore, there are many possible systems, each with n = EACN, available for crude oil recovery. In practice, however, the system variables may be manipulated to a limited extent only. The temperature of an oil field is fixed, and the surfactant concentration is limited by considerations of solubility and expense. The electrolyte concentration and type is partly determined by oilfield conditions and is limited by the effect on surfactant solubility. These limitations mean that many of the surfactants presently available on a large enough scale for use in low-tension flooding will not give minimum tensions in the range required (n of 6 to 9). This paper shows how minimal sigma's in the required range may be found for some of these "off-scale" surfactants when they are used in surfactant mixtures. The hypothesis tested here is that surfactant mixtures average in a manner analogous to the averaging of hydrocarbons in the oil phase. It will be shown that each surfactant component may be assigned an n value and that the alkane of minimum tension of a mixture of surfactants, (n), is then given by (2) where x is now the mole fraction of the ith component of the surfactant mixture. This greatly extends the number of surfactants that may be considered as candidates for use in low interfacial-tension flooding. SPEJ P. 122

Interrelation of Crude Oil and Rock Properties With the Recovery of Oil by Caustic Waterflooding

1977 ◽  
Vol 17 (04) ◽  
pp. 263-270 ◽  
Author(s):  
Robert Ehrlich ◽  
Robert J. Wygal
Keyword(s):  
Crude Oil ◽  
Reservoir Rock ◽  
Rock Properties ◽  
Core Material ◽  
Crude Oils ◽  
Active Materials ◽  
Interfacial Tensions ◽  
X Ray ◽  
Recovery Mechanisms ◽  
Surface Active

Abstract This paper describes a series of laboratory caustic (NaOH) waterfloods and related measurements using crude oils from 19 oil reservoirs. These were light (mostly,>30 degrees API) crudes mainly from South Louisiana and Texas, although crude oils from other areas also were tested. The waterfloods held core material (Berea sandstone), connate water (2-percent-NaCl brine) and other conditions (temperature, flow rate, aging time before flood) constant, and determined increased production due to NaOH injection for each crude oil. Relative permeability end-points before and after flooding were used to estimate initial and final wettabilities and, together with crude-oil acid numbers and interfacial tensions against NaOH solution, to infer the probable mechanism by which increased recovery was obtained. A series of laboratory NaOH depletion measurements by static and dynamic methods in core material from several oil-producing formations and in Berea sandstone is also described. Results are compared with those from similar measurements using pure clays and other minerals and with X-ray diffraction analysis of the core material. The following are observations from these tests.Crude oils with acid numbers greater than about 0.1 to a 0.2 mg KOH per gm of oil or interfacial tension against 0.1 percent NaOH less than about 0.5 dyne/cm gave significant caustic-waterflood increased production. There was no further correlation of increased production at higher acid numbers or lower interfacial tensions nor was there a correlation with the apparent initial rock wettability.Regardless of initial wettability or increased production, the cores are indicated to be water-wet production, the cores are indicated to be water-wet following NaOH waterflooding to a high water-oil ratio (WOR).Caustic consumption by reservoir rock is predictable from the formation mineral composition predictable from the formation mineral composition as determined by X-ray methods. Exceptions are noted where clay content is high and where trace amounts of gypsum are present. Introduction Crude oils containing naturally occurring organic acids will react with aqueous caustic solution to produce surface-active materials. These surfactants, produce surface-active materials. These surfactants, when generated during a caustic waterflood, can improve oil recovery over that of a normal waterflood by a number of mechanisms related to changes occurring at the oil-water and liquid-solid interfaces: interfacial-tension lowering, wettability change, changes in interface rheology, etc. The extent to which any of these mechanisms will be operative and the recovery improvement obtainable depends on, among other things, the amount and type of acids present, the initial formation wettability, the reservoir-rock pore geometry, and the extent to which it consumes caustic. The available literature describing mechanisms proposed for caustic-waterflooding improved recovery, proposed for caustic-waterflooding improved recovery, the conditions required for applicability, and the results of various laboratory and field studies have been surveyed most recently by Johnson. Some common currents of thought or implication in this literature and some common areas of uncertainty related to the effects of crude oil and reservoir rock properties on recovery mechanisms are listed below. properties on recovery mechanisms are listed below.The presence of acids in crude oil at some minimum level is an obvious necessary condition for improved recovery. Where emulsification is involved, minimum acid numbers ranging from 0.5 to 1.5 mg KOH per gm of oil have been suggested. No minimum has been stated for other recovery mechanisms. One might not expect such minimum requirements to be absolute since the quality of surfactants generated from these acids can vary widely among crude oils.Improved recovery by wettability alteration generally has been discussed in terms of a reversal from oil-wet to water-wet or vice versa. It has been implied that wettability reversal is required since capillary forces trapping oil are eliminated as the neutral wettability condition is traversed. SPEJ P. 263

A method for the calculation of surface and interfacial tensions from the shape of pendent drops

1968 ◽  
Vol 46 (24) ◽  
pp. 3918-3919 ◽  
Author(s):  
H. Lomas
Keyword(s):  
Interfacial Tension ◽  
Computer Program ◽  
Interfacial Tensions ◽  
Simple Computer ◽  
Capillary Equation ◽  
Simple Computer Program ◽  
Pendent Drop

A classical capillary equation is applied to the shape of the portion of a pendent drop on the opposite side to the source, and the interfacial tension is calculated by the use of a simple computer program.

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