Multiphase Microemulsion Systems

1976 ◽  
Vol 16 (03) ◽  
pp. 147-160 ◽  
Author(s):  
R.N. Healy ◽  
R.L. Reed ◽  
D.G. Stenmark
Keyword(s):  
Interfacial Tension ◽  
Physicochemical Properties ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Displacement Efficiency ◽  
Oil Composition ◽  
Alkyl Aryl ◽  
Optimal Salinity ◽  
Interfacial Tensions ◽  
Multiphase Behavior

Abstract Economical microemulsion flooding inevitably involves microemulsion phases immiscible with oil or water, or both; oil recovery is largely affected by displacement efficiency during the immiscible regime. Therefore, it is essential to understand the role of interfacial tension in relation to multiphase microemulsion behavior. Three basic types of multiphase systems are identified and used to label phase transitions that occur when changes are made in salinity, temperature, oil composition, surfactant structure, cosolvent, and dissolved solids in the aqueous phase. Directional effects of these changes on phase behavior, interfacial tension, and solubilization parameter are tabulated for the alkyl aryl sufonates studied. A relationship between interfacial tension and phase behavior is established. This provides the phase behavior is established. This provides the basis for a convenient method for preliminary screening of surfactants for oil recovery. Interfacial tensions were found to correlate with the solubilization parameter for the various microemulsion phases, a result that can substantially reduce the number of interfacial tensions that must be determined experimentally for a given application. Introduction A previous paper established that microemulsion flooding is a locally miscible process until slug breakdown and is an immiscible, rate-dependent displacement thereafter; furthermore, for an effective flood, most of the oil recovered is acquired during the immiscible regime. An extensive study of single-phase regions defined classes of micellar structures for a particular surfactant; however, it was subsequently shown these did not affect oil recovery, provided viscous, lamellar structures were avoided. Optimal salinity was introduced as defining a ternary diagram having the least extensive multiphase region, a desirable feature in that locally miscible displacement is prolonged. Immiscible displacement after slug breakdown is known to depend on interfacial tension through its inclusion in the capillary number. A brief study showed chat interfacial tension varied widely throughout the multiphase region; accordingly, it is anticipated that oil recovery will depend on details of multiphase behavior in relation to interfacial tension, as well as on injection composition. Consider a flood sufficiently advanced that the microemulsion slug has broken down. A microemulsion phase remains that is immiscible with water or oil, phase remains that is immiscible with water or oil, or both, and displacement has assumed an immiscible character. The problem is twofold: to design a microemulsion slug that effectively displaces oil at the front and that is effectively displaced by water at the back. Both aspects are essential and, therefore, both microemulsion-oil and microemulsion-water interfacial tensions must be very low. The condition where these two tensions are low and equal will be of particular significance. The purpose of this paper is to explore physicochemical properties of multiphase physicochemical properties of multiphase microemulsion systems with a view toward understanding immiscible aspects of microemulsion flooding, and with the expectation of developing systematic screening procedures useful for design of optimal floods. Equilibration is an essential part of this study. Even the simplest of these systems is so complex it may well happen that nonequilibrium effects will never be understood sufficiently to be usefully accommodated in mathematical simulation of microemulsion flooding. In any event, equilibration, although time consuming, leads to a coherent picture of multiphase behavior that can be correlated with flooding results. Multiphase behavior of "simple" ternary systems divides into three basic classes. Dependence of phase behavior on salinity, with respect to these phase behavior on salinity, with respect to these classes, leads to correlations of interfacial tension with the solubilization parameter. These correlations are studied in relation to surfactant structure, temperature, cosolvents, oil composition, and brine composition. Optimal salinity again plays an important role, especially in relation to interfacial tension. SPEJ P. 147

scholarly journals Physicochemical Properties and its Variation Law of Microemulsion Phase When Microemulsion Flooding

2021 ◽  
Vol 252 ◽  
pp. 02066
Author(s):  
Dongqi Wang ◽  
Daiyin Yin ◽  
Junda Wang
Keyword(s):  
Interfacial Tension ◽  
Physicochemical Properties ◽  
Phase Behavior ◽  
High Water ◽  
Microemulsion System ◽  
Composition Change ◽  
Displacement Efficiency ◽  
Characterization Methods ◽  
Phase Density ◽  
Research Results

The composition change of microemulsion system in microemulsion flooding will inevitably cause the change of phase behavior. Microemulsion with different phase types directly affects its performance and displacement efficiency of microemulsion flooding. Therefore, in order to accurately describe this change, this paper, starting from the composition of microemulsion, gives the physicochemical properties characterization methods of microemulsion phase density, viscosity and interfacial tension, and simulates the change of physicochemical properties of microemulsion phase caused by microemulsion entering the high water-oil ratio zone in the process of flooding. The research results are of great significance for screening microemulsion systems and determining the displacement efficiency.

Phase Behavior and Properties of a Petroleum Sulfonate Blend

1981 ◽  
Vol 21 (05) ◽  
pp. 573-580 ◽  
Author(s):  
J.H. Bae ◽  
C.B. Petrick
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Surfactant Solution ◽  
Phase Region ◽  
Salinity Range ◽  
Equal Weight ◽  
Optimal Salinity ◽  
Petroleum Sulfonate

Abstract A sulfonate system composed of Stepan Petrostep TM 465, Petrostep 420, and 1-pentanol was investigated. The system was found to give ultralow interfacial tension against crude oil in a reasonable range of salinity and sulfonate concentrations. It also was found that sulfonate partitioned predominantly into the microemulsion phase. However, a significant amount also partitioned into water and, at high salinity, into the oil phase. On the other hand, the oil-soluble 1-pentanol partitioned mostly into oil and microemulsion phases.The interfacial tension between excess oil and water phases was ultralow, in the range of 10-3 mN/m. The tensions were close to and paralleled those between the middle and water phases. The trend remained the same even when the alcohol content changed. This means that in the salinity range that produces a three-phase region, below the optimal salinity, the water phase effectively displaces both oil and middle phases, even though the oil may not be displaced effectively by the middle phase. The implication is that, from an interfacial tension point of view, the oil recovery would be more favorable in the salinity range below the optimal salinity with the mixed petroleum sulfonate system used here. This was confirmed by oil recovery tests in Berea cores. It also was concluded that the change in viscosity upon microemulsion formation might have a significant influence on the surfactant flood performance. Introduction During a surfactant flood, the injected slug of surfactant solution undergoes complex changes as it traverses the reservoir. The surfactant solution is diluted by mixing with reservoir oil and brine and by depletion of surfactant due to retention. Also, the reservoir salinity rarely is the same as that of the injected solution. Moreover, there is chromatographic separation of sulfonate and cosurfactant.When phase equilibrium between oil, brine, and injected surfactant is reached in the front portion of the slug, a microemulsion phase is formed. This phase behavior and its importance in oil recovery have been the subject of numerous papers in recent years. The microemulsion phase formed in the reservoir contacts fresh reservoir brine and oil and undergoes further changes. All these changes are accompanied by property changes of the phases that affect oil recovery.The objective of this paper is to investigate the properties of a blend of commercial petroleum sulfonates and its behavior in different environments. The phase volume behavior and changes in the properties of different phases and their effects on oil recovery were studied. This work was done as part of the design of a surfactant process for a field application. Therefore, a crude oil was used as the hydrocarbon phase. Experimental Procedures A blend of Petrostep 465 and 420 from Stepan Chemical Co. was used as the surfactant. An equal weight of each sulfonate on a 100% active basis was mixed. 1-pentanol from Union Carbide Corp. was used as a cosurfactant. Unless otherwise stated, a 50g/kg sulfonate concentration was used in the solution. We used symbols to denote the formulation. The first number in the symbol indicates the 1-pentanol concentration; the last number indicates the NaCl concentration. Thus, 15 P 10 means that the solution consists of 50 g/kg sulfonate, 15 g/kg 1-pentanol, and 10 g/kg NaCl. The sulfonate blend first was mixed with alcohol, and then the required amount of NaCl brine was added to make the solution. SPEJ P. 573^

Application of the Theory of Multicomponent, Multiphase Displacement to Three-Component, Two-Phase Surfactant Flooding

1981 ◽  
Vol 21 (02) ◽  
pp. 191-204 ◽  
Author(s):  
George J. Hirasaki
Keyword(s):  
Partition Coefficient ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Chromatographic Separation ◽  
Partition Coefficients ◽  
Phase System ◽  
Surfactant Flooding ◽  
Two Phase ◽  
Optimal Salinity ◽  
Interfacial Tensions

Abstract The theory presented in a companion paper is illustrated for the case of three-component, two-phase (i.e., constant-salinity) surfactant flooding. The utility of this method is that, in addition to computation of specific cases, it provides a general qualitative understanding of the displacement behavior for different phase diagrams and different injection compositions. The phase behavior can be classified as to whether the partition coefficient is less than or greater than unity. The injection composition of the slug can be classified as to whether it is aqueous or oleic and whether it is inside or outside the region of tieline extensions.The theory provides an understanding of the displacement mechanisms for the three-component, two-phase system as a function of phase behavior and injection composition. This understanding aids the interpretation of phenomena such as the effects of dispersion, salinity gradient, chromatographic separation, and polymer/surfactant interaction. Introduction The phase behavior of surfactant with oil and brine is the underlying phenomenon of most surfactant-flood design philosophies. The surfactant slugs have been formulated either as (1) surfactant in water, (2) surfactant in oil, or (3) microemulsions containing both water and oil. Recovery of oil is thought to occur by solubilization, oil swelling, miscible displacement, and/or low interfacial tensions. The low interfacial tensions occur in a salinity environment such that three phases can coexist. At higher salinities the surfactant is in the oleic phase, and at lower salinities it is in the aqueous phase.Some recent investigators have preferred designing their process at a constant salinity even though their experiments indicated better oil recovery with a salinity contrast. Glover et al. point out that the optimal salinity is not constant in brines containing divalent ions and that phase trapping can result in large retention of surfactant in a system that was at optimal salinity at injected conditions. Nelson and Pope have demonstrated that good oil recovery is possible in systems containing formation brine with 120,000 ppm TDS and 3,000 ppm divalent cations if the drive salinity is sufficiently low such that the surfactant partitions into the aqueous phase. Moreover, the peak surfactant concentration in the effluent occurred in the three-phase environment where the lowest interfacial tension usually occurs.The purpose of this work is to understand better the mechanism of multiphase, multicomponent displacement so that the phase behavior can be used to advantage. The approach used is to examine in detail the displacement mechanism and behavior of a two-phase, three-component system. This understanding will build a foundation for examining more complex systems.Earlier, Larson and Hirasaki showed effects of oil swelling and the retardation of the surfactant front due to the surfactant partitioning into the oleic phase. Recently, Larson extended the work to finite slugs including oleic slugs. He showed the conditions necessary to have miscible or piston-like displacement. His work showed that systems with large partition coefficients are more tolerant to dispersive mixing. We show in this paper that his observation was probably the consequence of having a phase diagram with a constant partition coefficient. Todd et al. show the effect of the partition coefficients on the chromatographic separation and retention for a two-component surfactant system. Pope et al. evaluated the sensitivity of the performance of a surfactant flood to a number of factors. SPEJ P. 191^

Investigation of Three-Phase Regions Formed by Petroleum Sulfonate Systems

1981 ◽  
Vol 21 (05) ◽  
pp. 581-592 ◽  
Author(s):  
Creed E. Blevins ◽  
G. Paul Willhite ◽  
Michael J. Michnick
Keyword(s):  
Interfacial Tension ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Phase Region ◽  
Phase Boundaries ◽  
Middle Phase ◽  
Optimal Salinity ◽  
Petroleum Sulfonate ◽  
Recovery Processes ◽  
Three Phase

Abstract The three-phase region of the Witco TRS 10-80 sulfonate/nonane/isopropanol (IPA)/2.7% brine system was investigated in detail. A method is described to locate phase boundaries on pseudoternary diagrams, which are slices of the tetrahedron used to display phase boundaries of the four-component system.The three-phase region is wedge-like in shape extending from near the hydrocarbon apex to a point near 20% alcohol on the brine/alcohol edge of the tetrahedron. It was found to be triangular in cross section on pseudoternary diagrams of constant brine content, with its base toward the nonane/brine/IPA face. The apex of the three-phase region is a curved line where the M, H + M, and M + W regions meet. On this line, the microemulsion (M*) is saturated with hydrocarbon, brine, and alcohol for a particular sulfonate content. A H + M region exists above the three-phase region, and an M + W region exists below it.Relationships were found between the alcohol concentration of the middle phase and the sulfonate/alcohol and sulfonate/hydrocarbon ratios in the middle phase. These correlations define the curve that represents the locus of saturated microemulsions in the quaternary phase diagram. Alcohol contents of excess oil and brine phases also were correlated with alcohol in the middle phase.Pseudoternary diagrams for sulfonates are presented to provide insight into the evolution of the three-phase region with salinity. Surfactants include Mahogany AA, Phillips 51918, Suntech V, and Stepan Petrostep(TM) 500. Differences between phase diagrams follow trends inferred from comparisons of equivalent weights, mono-/disulfonate content, optimal salinity, and EPACNUS values. Introduction The displacement of oil from a porous rock by microemulsions is a complex process. As the microemulsion flows through the rock, it mixes with and/or solubilizes oil and water. The composition of the microemulsion is altered by adsorption of sulfonate, leading to expulsion of water and/or oil. Multiphase regions are encountered where phases may flow at different velocities depending on the fluid/rock interactions. Knowledge of phase behavior of microemulsion systems is required to understand the displacement mechanisms, to model process performance, and to select suitable compositions for injection.Microemulsions used in oil recovery processes consist of five components: oil, water, salt, surfactant (usually a petroleum sulfonate and a cosurfactant (usually an alcohol). Brine frequently is considered to be a pseudocomponent. When this assumption is valid, a microemulsion may be studied as a four-component system.Windsor developed a qualitative explanation and classification scheme for microemulsion phase behavior. Healy and Reed showed that Windsor's concepts were applicable to microemulsions used in oil recovery processes. Healy et al. introduced the concept of optimal salinity to define a particular characteristic of surfactant system. The optimal salinity for phase behavior was defined as the salinity where the middle phase of a three-phase system has equal solubility of oil and brine. They also found that optimal salinity determined in this manner was close to the salinity where the interfacial tension between the upper and middle phases was equal to the interfacial tension between the middle and lower phases.Salager et al. developed a correlation of optimal salinity data for a particular surfactant. SPEJ P. 581^

A Study of Oil Displacement by Microemulsion Systems Mechanisms and Phase Behavior

1980 ◽  
Vol 20 (06) ◽  
pp. 459-472 ◽  
Author(s):  
G.P. Willhite ◽  
D.W. Green ◽  
D.M. Okoye ◽  
M.D. Looney
Keyword(s):  
Interfacial Tension ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Surfactant Solution ◽  
Residual Oil ◽  
Surfactant Flooding ◽  
Displacement Efficiency ◽  
High Concentration ◽  
The Core ◽  
Oil Displacement

Abstract Microemulsions located in a narrow single-phase region on the phase diagram for the quaternary system consisting of nonane, isopropyl alcohol, Witco TRS 10-80 petroleum sulfonate, and brine were used to investigate the effect of phase behavior on displacement efficiency of the micellar flooding process. Microemulsion floods were conducted at reservoir rates in 4-ft (1.22-m) Berea cores containing brine and residual nonane. Two floods were made using large (1.0-PV) slugs. A third flood used a 0.1-PV slug followed by a mobility buffer of polyacrylamide. Extensive analyses of the core effluents were made for water, nonane, alcohol, and mono- and polysulfonates. An oil bank developed which broke through at 0.08 to 0.1 PV, and 48 to 700/0 of the oil was recovered in this bank which preceeded breakthrough of monosulfonate and alcohol. Coincidental with the arrival of these components of the slug, the effluent became a milky white macroemulsion which partially separated upon standing. Additional oil was recovered with the macroemulsion. Ultimate recoveries were 90 to 100% of the residual oil. Low apparent interfacial tension was observed between the emulsion and nonane. Alcohol arrived in the effluent at the same time as monosulfonate even though there was extensive adsorption of the sulfonate. Further, alcohol appeared in the effluent well after sulfonate production had ceased, indicating retention of the alcohol in the core. A qualitative model describing the displacement process was inferred from the appearance of the produced fluids and the analyses of the effluents. Introduction Surfactant flooding (micellar or microemulsion) is one of the enhanced oil recovery methods being developed to recover residual oil left after waterflooding. Two approaches to surfactant flooding have evolved in practice. In one, relatively large volumes (0.25 PV) of low-concentration surfactant solution are used to create low-tension waterfloods.1,2 Oil is mobilized by reduction of interfacial tension to levels on the order of about 10−3 dyne/ cm (10−3 mN/m). The second approach involves the application of small volumes (0.03 to 0.1 PV) of high-concentration solutions.3,4 These solutions are miscible to some extent with the formation water and/or crude oil. Consequently, miscibility between the surfactant solution and oil and/or low interfacial tensions contribute to the oil displacement efficiency. The relative importance of these mechanisms has been the subject of several papers5,6 and discussions.7,8

Microemulsion Phase Behavior Observations, Thermodynamic Essentials, Mathematical Simulation

1981 ◽  
Vol 21 (06) ◽  
pp. 747-762 ◽  
Author(s):  
Karl E. Bennett ◽  
Craig H.K. Phelps ◽  
H. Ted Davis ◽  
L.E. Scriven
Keyword(s):  
Experimental Data ◽  
Phase Behavior ◽  
Experimental Studies ◽  
Mathematical Framework ◽  
Alkyl Aryl Sulfonate ◽  
Phase Volume ◽  
Displacement Efficiency ◽  
Alkyl Aryl ◽  
Theoretical Understanding ◽  
Tie Lines

Abstract The phase behavior of microemulsions of brine, hydrocarbon, alcohol, and a pure alkyl aryl sulfonate-sodium 4-(1-heptylnonyl) benzenesulfonate (SHBS or Texas 1) was investigated as a function of the concentration of salt (NaCl, MgCl2, or CaCl2), the hydrocarbon (n-alkanes, octane to hexadecane), the alcohol (butyl and amyl isomers), the concentration of surfactant, and temperature. The phase behavior mimics that of similar systems with the commercial surfactant Witco TRS 10–80. The phase volumes follow published trends, though with exceptions.A mathematical framework is presented for modeling phase behavior in a manner consistent with the thermodynamically required critical tie lines and plait point progressions from the critical endpoints. Hand's scheme for modeling binodals and Pope and Nelson's approach to modeling the evolution of the surfactant-rich third phase are extended to satisfy these requirements.An examination of model-generated progressions of ternary phase diagrams enhances understanding of the experimental data and reveals correlations of relative phase volumes (volume uptakes) with location of the mixing point (overall composition) relative to the height of the three-phase region and the locations of the critical tie lines (critical endpoints and conjugate phases). The correlations account, on thermodynamic grounds, for cases in which the surfactant is present in more than one phase or the phase volumes change discontinuously, both cases being observed in the experimental study. Introduction The phase behavior of a surfactant-based micellar formulation is one of the major factors governing the displacement efficiency of any chemical flooding process employing that formulation. Knowledge of phase behavior is, thus, important for the interpretation of laboratory core floods, the design of flooding processes, and the evaluation of field tests. Phase behavior is connected intimately with other determinants of the flooding process, such as interfacial tension and viscosity. Since the number of equilibrium phases and their volumes and appearances are easier to measure and observe than phase compositions, viscosities, and interfacial tensions, there is great interest in understanding the phase-volume/phase-property relationships. Commercial surfactants, such as Witco TRS 10-80, are sulfonates of crude or partially refined oil. While they seem to be the most economically practicable surfactants for micellar flooding, their behavior, particularly with crude oils and reservoir brines, can be difficult to interpret, the phases varying with time and from batch to batch. Phase behavior studies with a small number of components, in conjunction with a theoretical understanding of phase behavior progressions, can aid in understanding more complex behavior. In particular, one can begin to appreciate which seemingly abnormal experimental observations (e.g., surfactant present in more than one phase or a discontinuity in phase volume trends) are merely features of certain regions of any phase diagram and which are peculiar to the specific crude oil or commercial surfactant used in the study.We report here experimental studies of the phase behavior of microemulsions of a pure sulfonate surfactant (Texas 1), a single normal alkane hydrocarbon, a simple brine, and a small amount of a suitable alcohol as cosurfactant or cosolvent. The controlled variables are hydrocarbon chain length, alcohol, salinity, salt type (NaCl, MgCl2, or CaCl2), surfactant purity, surfactant concentration, and temperature. Many of these experimental data were presented earlier. SPEJ P. 747^

Estimation of Optimal Salinity and Solubilization Parameters for Alkylorthoxylene Sulfonate Mixtures

1977 ◽  
Vol 17 (03) ◽  
pp. 193-200 ◽  
Author(s):  
M.C. Puerto ◽  
W.W. Gale
Keyword(s):  
Molecular Weight ◽  
Enhanced Oil Recovery ◽  
Mole Fraction ◽  
Oil Recovery ◽  
Carbon Number ◽  
Constant Weight ◽  
Optimal Salinity ◽  
Interfacial Tensions ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Abstract Economic constraints are such that it is unlikely a pure surfactant will be used for major enhanced oil recovery projects. However, it is possible to manufacture at competitive prices classes of syntheic and natural petroleum sulfonates that have fairly narrow molecular-weight distributions. Under some reservoir conditions, one of these narrow-distribution sulfonates may serve quite well as the basic component of a surfactant flood, however, in many instances a mixture of two or more of these may be required. Since evaluation of a significant subset of "all possible combinations" is a formidable undertaking screening techniques must be established that can reduce the number of laboratory core floods required. It is well known that interfacial tension plays a dominant role in surfactant flooding. It has recently been shown that minimal interfacial tensions occur at optimal salinity, Cphi, where the solubilization parameters VO/Vs and Vw/Vs are equal. Additionally, it has been shown that interracial tensions are inversely proportional to the magnitude of the solubilization parameters. This paper demonstrates that optimal salinity and solubilization parameters for any mixture of orthoxylene sulfonates can be estimated by summation of mole-fraction-weighted component properties. Those properties, which could not be properties. Those properties, which could not be measured directly, were obtained by least-squares regression on mixture data. Moreover, for surfactants of known carbon number distributions, equations that are linear in mole fractions of components and logarithmic in alkyl carbon number were found to be excellent estimators of both Cphi and solubilization parameters evaluated at Cphi. parameters evaluated at Cphi. Optimal salinity and associated solubilization parameters were measured using constant weight parameters were measured using constant weight fractions of alcohol cosolvents and mixtures of seven products with narrow molecular weight distributions. The average alkyl carbon number of these products varied from about 8 to 19. Alkyl chain lengths of individual surfactant chemical species ranged from 6 to 24 carbon atoms. Introduction Optimal salinity and the amounts of oil and water contained in a microemulsion have been shown to play important roles in obtaining low interfacial tensions and high oil recoveries. Since economics of enhanced oil recovery projects demand use of inexpensive surfactants, broad-distribution products likely will be chosen. Knowledge of how to estimate optimal salinity and oil-water contents of microemulsions prepared from such products would reduce time involved in laboratory screening procedures. This paper presents a method for procedures. This paper presents a method for obtaining such estimates that should prove useful for all types of surfactant mixtures that involve homologous series. The basic concept used is that a given property of a mixture of components (Yi) is related to the sum of products of mole fraction of components in the mixture (Xij) and the "mixing value" of the property in question for that component (Y'j). In property in question for that component (Y'j). In other words, (1) This approach is similar, for example, to the pseudocritical method used by Kay to calculate pseudocritical method used by Kay to calculate gas deviation factors at high pressures. The properties of interest in this paper are optimal properties of interest in this paper are optimal salinity and solubilization parameters, Vo/Vs, and Vw/Vs, at optimal salinity. Two separate approaches were developed that depended on the degree of detail of the available surfactant-composition data. In the first approach, only average molecular weights of several surfactant products were assumed known. Optimal salinity and products were assumed known. Optimal salinity and solubilization parameters could be measured for some, but not all, of the products. Regression on mixture data was used to estimate these quantities for the remainder of the products. Those properties, either measured experimentally or estimated from mixture data, are referred to as surfactant product contributions since they can be used as mixing values of the property in question in Eq. 1 or Eq. 2. SPEJ P. 193

Asphaltene Deposition Induced by Carbon Oxide and its Influence on Displacement Efficiency

2012 ◽  
Vol 594-597 ◽  
pp. 2451-2454
Author(s):  
Feng Lan Zhao ◽  
Ji Rui Hou ◽  
Shi Jun Huang
Keyword(s):  
Crude Oil ◽  
Oil Recovery ◽  
Carbon Oxide ◽  
Viscosity Reduction ◽  
Core Flooding ◽  
Displacement Efficiency ◽  
Oil Composition ◽  
Oil Viscosity ◽  
Asphaltene Deposition ◽  
Total Oil

CO2is inclined to dissolve in crude oil in the reservoir condition and accordingly bring the changes in the crude oil composition, which will induce asphaltene deposition and following formation damage. In this paper, core flooding device is applied to study the effect of asphaltene deposition on flooding efficiency. From the flooding results, dissolution of CO2into oil leads to recovery increase because of crude oil viscosity reduction. But precipitated asphaltene particles may plug the pores and throats, which will make the flooding effects worse. Under the same experimental condition and with equivalent crude oil viscosity, the recovery of oil with higher proportion of precipitated asphaltene was relatively lower during the CO2flooding, so the asphltene precipitation would affect CO2displacement efficiSubscript textency and total oil recovery to some extent. Combination of static diffusion and dynamic oil flooding would provide basic parameters for further study of the CO2flooding mechanism and theoretical evidence for design of CO2flooding programs and forecasting of asphaltene deposition.

Favorable Attributes of Alkaline-Surfactant-Polymer Flooding

SPE Journal ◽  
2008 ◽  
Vol 13 (01) ◽  
pp. 5-16 ◽  
Author(s):  
Shunhua Liu ◽  
Danhua Zhang ◽  
Wei Yan ◽  
Maura Puerto ◽  
George J. Hirasaki ◽  
...  
Keyword(s):  
Crude Oil ◽  
Phase Behavior ◽  
Anionic Surfactants ◽  
Naphthenic Acids ◽  
Mobility Control ◽  
Alkaline Solutions ◽  
Synthetic Surfactant ◽  
Optimal Salinity ◽  
Interfacial Tensions ◽  
Alkaline Surfactant Polymer

Summary A laboratory study of the alkaline-surfactant-polymer (ASP) process was conducted. It was found from phase-behavior studies that for a given synthetic surfactant and crude oil containing naphthenic acids, optimal salinity depends only on the ratio of the moles of soap formed from the acids to the moles of synthetic surfactant present. Adsorption of anionic surfactants on carbonate surfaces is reduced substantially by sodium carbonate, but not by sodium hydroxide. The magnitude of the reduction with sodium carbonate decreases with increasing salinity. Particular attention was given to a surfactant blend of a propoxylated sulfate having a slightly branched C16-17 hydrocarbon chain and an internal olefin sulfonate. In contrast to alkyl/aryl sulfonates previously considered for EOR, alkaline solutions of this blend containing neither alcohol nor oil were single-phase micellar solutions at all salinities up to approximately optimal salinity with representative oils. Phase behavior with a west Texas crude oil at ambient temperature in the absence of alcohol was unusual in that colloidal material, perhaps another microemulsion having a higher soap content, was dispersed in the lower-phase microemulsion. Low interfacial tensions existed with the excess oil phase only when this material was present in sufficient amount in the spinning-drop device. Some birefringence was observed near and above optimal conditions. While this phase behavior is somewhat different from the conventional Winsor phase sequence, overall solubilization of oil and brine for this system was high, leading to low interfacial tensions over a wide salinity range and to excellent oil recovery in both dolomite and silica sandpacks. The sandpack experiments were performed with surfactant concentrations as low as 0.2 wt% and at a salinity well below optimal for the injected surfactant. It was necessary that sufficient polymer be present to provide adequate mobility control, and that salinity be below the value at which phase separation occurred in the polymer/surfactant solution. A 1D simulator was developed to model the process. By calculating transport of soap formed from the crude oil and injected surfactant separately, it showed that injection below optimal salinity was successful because a gradient in local soap-to-surfactant ratio developed during the process. This gradient increases robustness of the process in a manner similar to that of a salinity gradient in a conventional surfactant process. Predictions of the simulator were in excellent agreement with the sandpack results. Background Although both injection of surfactants and injection of alkaline solutions to convert naturally occurring naphthenic acids in crude oils to soaps have long been suggested as methods to increase oil recovery, key concepts such as the need to achieve ultralow interfacial tensions and the means for doing so using microemulsions were not clarified until a period of intensive research between approximately 1960 and 1985 (Reed and Healy 1977; Miller and Qutubuddin 1987; Lake 1989). Most of the work during that period was directed toward developing micellar-polymer processes to recover residual oil from sandstone formations using anionic surfactants. However, Nelson et al. (1984) recognized that in most cases the soaps formed by injecting alkali would not be at the "optimal" conditions needed to achieve low tensions. They proposed that a relatively small amount of a suitable surfactant be injected with the alkali so that the surfactant/soap mixture would be optimal at reservoir conditions. With polymer added for mobility control, the process would be an alkaline-surfactant-polymer (ASP) flood. The use of alkali also reduces adsorption of anionic surfactants on sandstones because the high pH reverses the charge of the positively charged clay sites where adsorption occurs. The initial portion of a Shell field test, which did not use polymer, demonstated that residual oil could be displaced by an alkaline-surfactant process (Falls et al. 1994). Several ASP field projects have been conducted with some success in recent years in the US (Vargo et al. 2000; Wyatt et al. 2002). Pilot ASP tests in China have recovered more than 20% OOIP in some cases, but the process has not yet been applied there on a large scale (Chang et al. 2006).

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