The Effect of Several Polymers on the Phase Behavior of Micellar Fluids

Abstract We made static measurements of the phase volumes of mixtures of surfactant, polymer, alcohol, water, oil, sodium chloride, and in some cases polymer additives. We also made a limited number of viscosity, phase concentration, and interfacial tension (IFT) measurements. The purpose was to determine systematically the effect of various polymers on the phase behavior of various surfactant formulations. We made measurements with and without oil (n-octane and n-octane/benzene mixtures) across a range of salinity appropriate to the particular surfactant at temperatures between 24 and 75 degrees C. Introduction The oil-free (i.e., no added oil) solutions showed a characteristic phase separation into an aqueous surfactant-rich phase and an aqueous polymer-rich phase at some sufficiently high salinity (NaCl concentration), which we call the critical electrolyte concentration (CEC). The CEC was found to be a characteristic of a given surfactant/alcohol combination that shifts with the solubility of the surfactant qualitatively the same way as does the optimal salinity: but the CEC was found independent of the polymer type, polymer concentration (between the 100- and 1,000-ppm limits investigated), and surfactant concentration. The CEC increases with increasing temperature for the anionic surfactants and decreases with increasing temperature for the nonionic surfactants. When oil was added to the mixtures, an entirely different pattern of phase behavior was observed. As salinity increases, the particular formulations form the typical sequence of lower-phase microemulsion and excess oil, middle-phase microemulsion. excess oil, and excess brine: and upper-phase microemulsion and excess brine. The sequence with polymer was precisely the same over most of the salinity range but deviated over a limited range of salinity; the three-phase region simply shifted a small distance to the left on the salinity scale. Also, and probably more significantly, some of the aqueous phases in the critical region of the shift (which is also just above oil-free CEC salinity) were found to be gel-like in nature. These apparently occur under conditions such that the polymer concentration in the excess brine of the three-phase systems becomes very high because almost all the polymer is always in the brine phase, even when the brine phase is very small. Thus an overall 1,000 ppm of polymer easily can be concentrated to 10,000 ppm or more. One of the most remarkable aspects of the phase behavior of the surfactant/polymer systems is that the same patterns are observed for all combinations of anionic and nonionic surfactants and polymers. Also, little difference was observed in the IFT values with and without polymer. The three-phase systems still exhibited ultralow IFT values. Obviously, significant differences did occur in the brine viscosities when polymer was added. The polymer-free mixtures were themselves quite viscous, however, and the viscosity of the oil-free surfactant-rich phases (above the CEC) was significantly higher when the phases were in equilibrium with a polymer-rich aqueous phase, even though they apparently contained almost no polymer. We found that the polymer-rich phases had normal viscosities, as judged by the same polymer in the same brine at the expected concentration, assuming all the polymer was in the polymer-rich phase. The effect of polymer on the systems with oil was to increase the viscosity of the water-rich phase only, with little effect on the microemulsion phase unless it was the water-rich phase. SPEJ P. 816^

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Mixing Rules for Optimum Phase-Behavior Formulations of Surfactant/Oil/Water Systems

Society of Petroleum Engineers Journal ◽

10.2118/7584-pa ◽

1979 ◽

Vol 19 (05) ◽

pp. 271-278 ◽

Cited By ~ 101

Author(s):

J.L. Salager ◽

M. Bourrel ◽

R.S. Schechter ◽

W.H. Wade

Keyword(s):

Phase Behavior ◽

Oil Recovery ◽

Practical Interest ◽

Phase Region ◽

Salinity Range ◽

Mixing Rules ◽

Recovery Efficiency ◽

Middle Phase ◽

Rich Phase ◽

Three Phase

Abstract Many formulations used in surfactant flooding involve blends of surfactants designed to glue the best oil-recovery efficiency. Because oil-recovery efficiency usually is presumed to relate closely to surfactant/brine/oil phase behavior, it is of interest to understand the effect of mixing surfactants or of mixing oils on this phase behavior.We show that a correlation defining optimal behavior as a function of salinity, alcohol type and concentration, temperature, WOR (water/oil ratio), and oil type can be extended to mixtures of sulfonated surfactants and to those of sulfonates with sulfates and of sulfonates with alkanoates, provided the proper mixing rules are observed. provided the proper mixing rules are observed. The mixing rules apply to some mixtures of anionic and nonionic surfactants, but not to all. These mixtures exhibit some properties that may be of practical interest, such as increased salinity and practical interest, such as increased salinity and temperature tolerance. Introduction Recent studies have shown that formulation of the surfactant/brine/oil system is a key factor governing the performance of microemulsions designed to recover residual oil. These studies demonstrate that all optimal formulations exhibit characteristic properties that are remarkably similar. In general, properties that are remarkably similar. In general, the optimal microemulsion can solubilize large quantities of oil and connate water; in the presence of excess quantities of oil and water, a third surfactant-rich middle phase is formed. The interfacial tensions (IFT's) between the excess phases and the surfactant-rich phase are both low - about 10 dyne/cm (10 mN/m). Given an oil/brine system from a particular reservoir, one can achieve this formulation by varying the surfactant or the cosurfactant. Different oils, brines, or temperatures require formulations correspondingly altered to maintain optimal conditions. Previous studies have shown that the three-phase region exists over a range of values when one parameter, such as cosurfactant concentration, parameter, such as cosurfactant concentration, salinity, temperature, etc., is varied systematically (often called a scan). Thus, some ambiguity may exist with regard to the selection of those parameters representing the optimal formulation. Clearly, the optimum is that which recovers the most oil. However, tests are laborious, difficult to reproduce precisely, and sensitive to other factors, such as precisely, and sensitive to other factors, such as mobility, surfactant retention, wettability, etc. Therefore, it is desirable to impose an alternative definition that can be used for screening, though the final design still is dictated by core floods.Healy and Reeds have shown that the optimal formulation for oil recovery closely corresponds to that for which the IFT's between the excess oil and water phases and the surfactant-rich phase are equal. An almost equivalent criterion also was shown to be that point in the three-phase region for which the volume of oil solubilized into the middle phase equals the volume of brine. Furthermore, Salager et al. have used still another criterion that seems to be essentially equivalent to those used by Healy and Reed - an optimal salinity is defined as the midpoint of the salinity range for which the system exhibits three phases.These criteria are useful because they permit the screening of microemulsion systems using simple laboratory tests. SPEJ P. 271

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The nature of the middle phase in three-phase micellar systems at phase behavior optimal salinity

Journal of Colloid and Interface Science ◽

10.1016/0021-9797(84)90317-5 ◽

1984 ◽

Vol 97 (2) ◽

pp. 456-464 ◽

Cited By ~ 14

Author(s):

Milton J Rosen ◽

Zhi-Ping Li

Keyword(s):

Phase Behavior ◽

Middle Phase ◽

Optimal Salinity ◽

Micellar Systems ◽

Three Phase

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Phase Behavior and Properties of a Petroleum Sulfonate Blend

Society of Petroleum Engineers Journal ◽

10.2118/8985-pa ◽

1981 ◽

Vol 21 (05) ◽

pp. 573-580 ◽

Cited By ~ 4

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^

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Equilibrium of a Microemulsion That Coexists With Oil or Brine

Society of Petroleum Engineers Journal ◽

10.2118/10728-pa ◽

1983 ◽

Vol 23 (05) ◽

pp. 829-847 ◽

Cited By ~ 35

Author(s):

Chun Huh

Keyword(s):

Phase Behavior ◽

Chain Length ◽

Phase State ◽

Water Soluble ◽

The Other ◽

Ionic Surfactants ◽

Middle Phase ◽

Lower Phase ◽

Optimal Salinity ◽

Drop Radius

Huh, Chun; SPE; Exxon Production Research Co. Abstract When salinity, or an equivalent variable, is increased, microemulsions generally undergo orderly transitions from a lower-to middle- to upper-phase. Even though the significance of such multiphase behavior has been well recognized in the design of surfactant flood processes, their quantitative nature in terms of the molecular structures of the surfactant lipophile, hydrophile, and the oil and brine salinity has not been fully understood. A theory of lower- and upper-phase microemulsions that gives reasonable predictions of their interfacial tensions (IFT's) and phase behavior is presented. In the theory, the surfactant monomers adsorbed at oil/brine interface cause the interface to bend as a result of an imbalance between the hydrophile/brine interaction on the one hand and lipophile/oil interaction on the other. With sufficient imbalance, high local curvature causes small drops of one phase to disperse into the other. In addition, interactions between these drops are taken into account for the microemulsion equilibrium. The theory also offers a possibility of being able to describe the hydrophile/lipophile-balanced state (optimal salinity state of Healy and Reed) in terms of the tendency of surfactant layer at the oil/brine interface to bend. Introduction Understanding the phase behavior of microemulsions is an important step in designing surfactant flooding processes and interpreting the results when they are applied to recover tertiary oil. It is well established that the phase behavior of many microemulsion systems, even those containing a large phase behavior of many microemulsion systems, even those containing a large number of different components can be represented qualitatively using pseudoternary diagrams similar to those in Fig. 1. Fig. 1a shows the pseudoternary diagrams similar to those in Fig. 1. Fig. 1a shows the lower-phase microemulsion in equilibrium with excess oil, Figs. 1b and 1c the middle-phase microemulsion in equilibrium with both oil and brine, and Fig. 1d the upper-phase microemulsion coexistent with excess water. Even though not all microemulsions conform to this simple picture, it serves as a good approximation frequently enough to use it as a basis for discussing microemulsion phase behavior. Transitions such as those shown by Fig. 1 can be produced by changing any of a large number of variables in a systematic manner. The phase shifts from "a" to "d" generally occur with increases in the salinity of the brine, the alkyl chain length of the surfactant, the aromaticity of the oil, the addition of a highly oil- soluble alcohol and a temperature increase (for non-ionic surfactants). The shifts also occur with decreases in the chain length of oil, the number of hydrophilic groups (e.g., ethylene oxide) of the surfactant, the addition of a highly water-soluble alcohol, and a temperature decrease (for most ionic surfactants). Since microemulsion phase transitions will be determined by the manner in which microemulsion structure depends on changes in the variables described above, many experimental studies have been made to determine microemulsion structure. Ultracentrifuge and light-scattering measurements show that the lower-phase microemulsion consists of spherical oil drops with radius of about 50 to 1,000 k in water. As it moves toward the middle-phase state (see Figs. 1a and 1b), the drop radius grows. On the other hand, the upper-phase microemulsion consists of small water drops in oil, and as it moves toward the middle-phase state (Figs. 1c and 1d), the drop radius again grows. Very little is known about the structure of middle-phase microemulsions. SPEJ p. 829

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Criteria for Structuring Surfactants To Maximize Solubilization of Oil and Water: Part 1-Commercial Nonionics

Society of Petroleum Engineers Journal ◽

10.2118/9815-pa ◽

1982 ◽

Vol 22 (05) ◽

pp. 743-749 ◽

Cited By ~ 19

Author(s):

Alain Graciaa ◽

Lester N. Fortney ◽

Robert S. Schechter ◽

William H. Wade ◽

Seang Yiv

Keyword(s):

Phase Behavior ◽

Oil Recovery ◽

Nonionic Surfactants ◽

Phase Region ◽

Microemulsion System ◽

Middle Phase ◽

Optimal Salinity ◽

Surfactant System ◽

Hydrophilic Lipophilic Balance ◽

Surfactant Systems

Abstract The phase behavior of nonionic surfactants having the same hydrophilic/lipophilic balance (HLB) but differing molecular weights has been studied. It is shown that the optimal alkane carbon number (ACN) depends on the HLB, but that increasing the hydrophobe molecular weight narrows the middle phase region, increases the solubilization parameter, and decreases the interfacial tension (IFT). We found that the width of the three-phase region is in simple inverse proportion to the solubilization parameter at optimal salinity and that the multiple of IFT times the square of the solubilization is a constant. We also found it possible to synthesize nonionics that rival anionics in the properties mentioned above. Introduction There is increasing evidence that the phase behavior of surfactant/oil/brine systems and the efficiency of oil recovery with micellar solutions are connected intimately. For instance, laboratory core floods have shown that surfactant systems exhibit maximum oil recovery at the optimal salinity. The concept of optimal salinity, introduced by Healy and Reed, is especially useful because it pen-nits screening of surfactant systems by relatively simple experiments requiring the observation of the number and the types of phases that coexist at equilibrium when surfactant/oil/brine mixtures are blended. Optimal salinity, defined as that middle-phase microemulsion system containing equal volumes of oil and water, is not difficult to determine, and, thus, conditions for the most efficient surfactant system can be established. It is now well known that many different surfactant systems have the same optimal salinity. Further, it generally has been assumed, but not definitely established by laboratory experiments that the preferred surfactant system, selected from a group of systems having the same optimal salinity, will be that which solubilizes the largest volume of oil and brine per unit mass of surfactant. We do not necessarily subscribe to this simple view. since there are many factors other than solubilization (such as surfactatant retention) that may influence oil recovery efficiency however, all other factors being equal, it is reasonable to attempt to maximize solubilization, especially because it has been found synonymous with minimal IFT's-an equally important factor governing effectiveness of oil recovery. This paper seeks to identify some surfactant structural features that will lead to increased solubilization and decreased IFT. We have addressed this important question in past publications but have met with only limited success. The difficulty has been that changing the surfactant structure dictates that a second corresponding change be made so that the resulting system would remain optimal. For instance, one can increase the length of the hydrocarbon tail of the surfactant molecule and at the same time compensate for this change either by decreasing the amount of hydrophobic alcohol added to the system or by decreasing the salinity of the system. The results obtained in this manner have remained difficult to interpret because all changes can and most often do alter the solubilization of oil and water in the middle-phase microemulsion. Therefore, it was not possible to separate that pan of the resulting solubilization change caused strictly by the modification of the surfactant structure. In the study discussed here, we made compensating changes in the surfactant structure, keeping all other variables fixed. For nonionic surfactants, compensating changes can be made in several ways. SPEJ P. 743^

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Investigation of Three-Phase Regions Formed by Petroleum Sulfonate Systems

Society of Petroleum Engineers Journal ◽

10.2118/8260-pa ◽

1981 ◽

Vol 21 (05) ◽

pp. 581-592 ◽

Cited By ~ 2

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^

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Book review: Short-Circuit Currents in Three-Phase Systems

IEE Proceedings C Generation Transmission and Distribution ◽

10.1049/ip-c.1986.0042 ◽

1986 ◽

Vol 133 (5) ◽

pp. 292

Author(s):

N.M. Levy

Keyword(s):

Short Circuit ◽

Three Phase ◽

Phase Systems ◽

Short Circuit Currents

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Geometric Algebra Framework Applied to Symmetrical Balanced Three-Phase Systems for Sinusoidal and Non-Sinusoidal Voltage Supply

Mathematics ◽

10.3390/math9111259 ◽

2021 ◽

Vol 9 (11) ◽

pp. 1259

Author(s):

Francisco G. Montoya ◽

Raúl Baños ◽

Alfredo Alcayde ◽

Francisco Manuel Arrabal-Campos ◽

Javier Roldán Roldán Pérez

Keyword(s):

Geometric Algebra ◽

Dimensional Euclidean Space ◽

Active Components ◽

Electrical Circuits ◽

Current Harmonics ◽

Operation Conditions ◽

Multiple Phase ◽

Three Phase ◽

Phase Systems ◽

Definition Of

This paper presents a new framework based on geometric algebra (GA) to solve and analyse three-phase balanced electrical circuits under sinusoidal and non-sinusoidal conditions. The proposed approach is an exploratory application of the geometric algebra power theory (GAPoT) to multiple-phase systems. A definition of geometric apparent power for three-phase systems, that complies with the energy conservation principle, is also introduced. Power calculations are performed in a multi-dimensional Euclidean space where cross effects between voltage and current harmonics are taken into consideration. By using the proposed framework, the current can be easily geometrically decomposed into active- and non-active components for current compensation purposes. The paper includes detailed examples in which electrical circuits are solved and the results are analysed. This work is a first step towards a more advanced polyphase proposal that can be applied to systems under real operation conditions, where unbalance and asymmetry is considered.

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