Ternary Phase Behavior at High Temperatures

1968 ◽  
Vol 8 (04) ◽  
pp. 381-388 ◽  
Author(s):  
Leonal V. Pirela ◽  
S.M. Farouq Ali
Keyword(s):  
Ternary System ◽  
Distribution Coefficient ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Ternary Phase ◽  
Elevated Temperatures ◽  
Thermal Recovery ◽  
Basic Information ◽  
Plait Point ◽  
Tie Lines

Abstract Some interest has been expressed recently in the application of solvents in conjunction with a thermal drive, such as a steamflood. At least one field project of this type bas been reported. This paper makes the first attempt to provide some of paper makes the first attempt to provide some of the basic information necessary for choosing a solvent for such an application. Results of displacements conducted at elevated temperatures are also discussed. This paper shows that, in the case of alcohol-hydrocarbon-water or brine ternary systems, the system miscibility may increase, decrease, or both increase and decrease within the same system when the temperature increases. The distribution coefficient was consistently found to increase in favor of the oleic phase with an increase in temperature, which is advantageous from the standpoint of oil recovery. Results of solvent displacements in a sandstone core showed that even a relatively small temperature effect in the favorable direction (increase in miscibility and distribution coefficient) can lead to a 50 percent increase in oil recover, ton the other hand if the system miscibility decreases with the temperature, even though the distribution coefficient increases, the oil recovery at the higher temperature may not increase. Introduction Miscible displacement has been the subject of many investigations. Miscible-phase solvent flooding, employing solvents such as alcohols that are miscible with both oil and water, has received considerable attention. Investigations conducted by Gatlin and Slobod, Taber, Kamath and Reed, Holm and Csaszar, and Farouq Ali and Stahl have helped in understanding the mechanism of solvent flooding. While the use of alcohols and similar solvents as oil recovery agents is economically unattractive these solvents nevertheless provide a means of understanding the mechanistic aspects of important miscible-phase oil recovery processes such as the Maraflood process (discussed by Gogarty). As shown by Taber et al., the phase behavior of a solvent-oil-water system is of utmost importance in determining the efficiency of the oil displacement. This paper makes the first attempt to obtain the ternary phase behavior data for nine alcohol-hydrocarbon-water/brine systems at elevated temperatures. Results of core tests at elevated temperatures are also presented which corroborate the effect of temperature on oil recovery, as judged on the basis of phase-behavior data. The use of solvents at elevated temperatures has been suggested earlier by Farouq Ali. At least one field test of this type has been reported. With the widespread use of thermal recovery techniques, it is possible in some situations (especially in steamflooding) that the use of a suitable solvent in conjunction with the heat carrier may be economically feasible. This paper attempts to provide some of the basic information needed for judging such feasibility. LOCATION OF THE PLAIT POINT The phase behavior of a typical ternary system consisting of a solvent, hydrocarbon and brine (or water) can be represented by a triangular diagram such as the one shown in Fig. 1 (for temperature T,). Point P on the bimodal curve represents the plait point, being the limit of tie lines such as plait point, being the limit of tie lines such as YlY2,. The compositions of the coexisting oleic and aqueous phases are given by points Y2 and Y1, respectively, for any mixture composition along Y1Y2. The characteristics of ternary diagrams have been discussed by Findlay and others. Taber et al. have shown that the position of the plait point in a particular ternary system plays the plait point in a particular ternary system plays the decisive role in determining whether or not the oleic phase would be displaced in a continuous manner phase would be displaced in a continuous manner during an alcohol displacement. SPEJ P. 381

A Negative-Flash Tie-Simplex Approach for Multiphase Reservoir Simulation

SPE Journal ◽  
2013 ◽  
Vol 18 (06) ◽  
pp. 1140-1149 ◽  
Author(s):  
Alireza Iranshahr ◽  
Denis V. Voskov ◽  
Hamdi A. Tchelepi
Keyword(s):  
Phase Behavior ◽  
Oil Recovery ◽  
Large Scale ◽  
Flow Simulation ◽  
Steam Injection ◽  
Compositional Simulation ◽  
Reservoir Flow ◽  
Wide Range ◽  
Tie Lines ◽  
Eor Processes

Summary Enhanced Oil Recovery (EOR) processes usually involve complex phase behavior between the injected fluid (e.g., steam, hydrocarbon, CO2, sour gas) and the in-situ rock-fluid system. Several fundamental questions remain regarding Equation-of-State (EOS) computations for mixtures that can form three, or more, phases at equilibrium. In addition, numerical and computational issues related to the proper coupling of the thermodynamic phase behavior with multi-component transport must be resolved to accurately and efficiently model the behavior of large-scale EOR processes. Previous work has shown that the adaptive tabulation of tie-simplexes in the course of a compositional simulation is a reliable alternative to the conventional EOS-based compositional simulation. In this paper, we present the numerical results of reservoir flow simulation with adaptive tie-simplex parameterization of the compositional space. We study the behavior of thermal-compositional reservoir displacement processes across a wide range of fluid mixtures, pressures, and temperatures. We show that our approach rigorously accounts for tie-simplex degeneration across phase boundaries. We also focus on the complex behavior of the tie-triangles and tie-lines associated with three-phase, steam injection problems in heterogeneous formations. Our studies indicate that the tie-simplex based simulation is a potential approach for fast EOS modeling of complex EOR processes.

The Influence of Phase Behavior on Surfactant Flooding

1979 ◽  
Vol 19 (06) ◽  
pp. 411-422 ◽  
Author(s):  
Ron G. Larson
Keyword(s):  
Porous Media ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Method Of Characteristics ◽  
Ternary Diagram ◽  
Base Case ◽  
Surfactant Flooding ◽  
Miscible Displacements ◽  
Tie Lines ◽  
Shed Light

Abstract This paper analyzes by mathematical modeling the role of phase behavior in surfactant flooding. In the absence of dispersion, miscible, immiscible, and semimiscible displacements are distinguished by the position of the injected composition relative to the position of the injected composition relative to the binodal envelope and extended tie lines. Even with dispersion, these concepts prove useful in analyzing slug miscibility breakdown in surfactant floods. Introduction Two design philosophies of tertiary oil recovery by surfactant flooding exist. In one, the chemical slug is designed to be miscible in some proportions with reservoir oil and brine, the goal being miscible displacement of resident oil. The second philosophy is to attain, rather than miscibility, philosophy is to attain, rather than miscibility, ultralow interfacial tension (IFT) between the slug fluid and resident oil. Correlations obtained by immiscible displacements of oil from natural and artificial porous media show that the saturation of residual oil (i.e. trapped, unrecoverable oil) decreases as IFT decreases. In reality, the distinction between philosophies is a matter of degree. Miscible displacements have regions of immiscibility. (e.g., the oil/brine bank). Furthermore, advocates of miscible displacements concede that breakdown into immiscible displacement occurs in the later stages of their processes; others argue that the breakdown occurs processes; others argue that the breakdown occurs early and that miscible displacements are, by and large, immiscible. On the other hand, since most slug formulations advocated by both schools are single phases capable of absorbing some amount of oil and phases capable of absorbing some amount of oil and brine without splitting into multiple phases, even chemical flood displacements designed to be immiscible are miscible for some time, however short. A related area of contention concerns the alleged advantages or disadvantages of formulating oil-rich, as opposed to brine-rich, slugs. Another area of contention concerns whether small, high-concentration chemical slugs are preferred to larger, lower-concentration slugs. The purpose of this paper is to shed light on these questions by paper is to shed light on these questions by incorporating equilibrium phase concepts as represented on a ternary diagram into the simulation of surfactant flood displacements. This study indicates that immiscible and miscible displacements are, in fact, closely related. Specifically, miscible recovery of oil is enhanced if the multiphase region of the ternary diagram contains a substantial subregion of ultralow tension. Furthermore, the success of miscible displacements is affected strongly not only by the position of the slug composition relative to the multiphase envelope on a ternary diagram but also by the position of slug composition relative to the tie lines, with better oil recovery attained when the injected composition point lies away from the region through which point lies away from the region through which extended tie lines pass. Thus, this study stresses the importance of the partition coefficient, a parameter shown to be important in an earlier study. For the purpose of this study, two simulation techniques for three-component, one- and two-phase flow in porous media were developed, each with its own restrictions. The first, a method-of-characteristics scheme (extended from a method developed earlier) allows phase volumes to change by solubilization of components phase volumes to change by solubilization of components but considers only continuous injection of micellar fluid, not the more realistic slug injection. The second method is a finite-difference approach that handles slug injection and solubilization and builds in dispersion, which cannot be considered when the method of characteristics is used. Because of the large number of parameters that arise in this study, base-case values (Table 1) of all parameters have been selected. For all results given in parameters have been selected. For all results given in this paper, the value of each parameter is the base-case value, unless otherwise specified. SPEJ P. 411

Nonlinear Formulation Based on an Equation-of-State Free Method for Compositional Flow Simulation

SPE Journal ◽  
2012 ◽  
Vol 18 (02) ◽  
pp. 264-273 ◽  
Author(s):  
R.. Zaydullin ◽  
D.V.. V. Voskov ◽  
H.A.. A. Tchelepi
Keyword(s):  
Multiphase Flow ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Equilibrium Phase ◽  
Computational Cost ◽  
Practical Interest ◽  
Flow Simulation ◽  
Flow In Porous Media ◽  
Compositional Simulation ◽  
Tie Lines

Summary Compositional simulation is necessary for modeling complex enhanced oil recovery (EOR) processes. For accurate simulation of compositional processes, we need to resolve the coupling of the nonlinear conservation laws, which describe multiphase flow and transport, with the equilibrium phase behavior constraints. The complexity of the problem requires extensive computations and consumes significant time. This paper presents a new framework for the general compositional problem associated with multicomponent multiphase flow in porous media. Here, adaptive construction and interpolation using the supporting tie lines are used to obtain the phase state and the phase compositions. For the parameterization of the full solution of a complex compositional problem, we need only a limited number of supporting tie lines in the compositional space. The parameterized tie lines are triangulated using Delaunay tessellation, and natural-neighbor interpolation is used inside the simplexes. Then, the computation of the phase behavior in the course of a simulation becomes an iteration-free, table look-up procedure. The treatment of nonlinearities associated with complex thermodynamic behavior of the fluid is based on the new set of unknowns—tie-line parameters that allow for efficient representation of the subcritical region. For the supercritical region, we use the standard compositional variable set based on the overall composition. The efficiency and accuracy of the method are demonstrated for several multidimensional compositional problems of practical interest. In terms of the computational cost of the thermodynamic calculations, the proposed method shows results comparable to those of state-of-the-art techniques. Moreover, the method shows better nonlinear convergence in the case of near-miscible gas-injection simulation.

Investigations of Miscible Displacements of Aqueous and Oleic Phases From Porous Media

1964 ◽  
Vol 4 (01) ◽  
pp. 37-48 ◽  
Author(s):  
J.J. Taber ◽  
W.K. Meyer
Keyword(s):  
Phase Diagram ◽  
Oil Recovery ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Wide Spectrum ◽  
Oil Viscosity ◽  
Plait Point ◽  
Miscible Displacements ◽  
Wide Range ◽  
Composition Path

Abstract Experiments on consolidated sandstones have shown that a variety of conditions are responsible for the wide range of behavior observed when oil and water are displaced simultaneously by a solvent which is miscible with both. The type of displacement is influenced most strongly by the relation between the plait point of the ternary phase diagram and the composition path followed by the system as it achieves miscibility. Neglecting viscosity, the displacement becomes less efficient as the distance between the composition path and plait point is increased in either direction so that a very wide spectrum of displacements is possible with different alcohol, oil and brine systems. It is possible by choosing various composition paths as miscibility is achieved to exercise some control over the actual displacement mechanism. Control over the composition path is exercised by adding oil or water in specific amounts to the alcohol prior to its injection into the porous medium, This technique apparently makes it possible to obtain piston-like displacements with systems which are usually characterized by the efficient displacement of only one of the two phases i.e., either oil or water, while the other phase lags behind. However, the simultaneous displacement of oil and water is not as efficient as other miscible displacements at a similar mobility ratio. The evidence indicates that both oil and water "leak" into the alcohol "piston" in compensating amounts. With oils of low viscosities the displacement is inefficient because the low oil saturation in the stabilized bank causes oil to be trapped by water before miscibility is attained. Introduction The simultaneous displacement of oil and water by solvents such as alcohol has been investigated in the laboratory and in the field. The laboratory workers investigating all-liquid miscible systems have recognized the great importance that the nature of the triangular phase diagram exerts on the efficiency of the miscible displacement. Gatlin and Slobod pointed out that displacement efficiency will be improved if miscibility can be retained for long periods and that this behavior tends to be followed if the applicable phase diagrams have very low binodal curves. In their unconsolidated sand tests the alcohol was considered an ideal miscible piston displacing both oil and water phases. Later workers have pointed out that an important feature of the phase diagram as far as oil recovery is concerned is the location of the plait point. This is particularly true in the case of consolidated sandstone. Since the original discussion of this effect, the importance of plait point location has been confirmed and discussed by other authors. The early workers recognized that the position of the plait point could be altered by changing the oil or the alcohol used in an experiment. In addition, recent work has demonstrated that the plait point can be shifted by altering the nature and concentration of dissolved salts in the aqueous phase. However, the entire scope of the relationship between displacement and plait point has not been discussed previously and a technique for changing the composition path as miscibility is achieved in a particular ternary system, i.e., oil, water and solvent, has not been demonstrated. * The importance of oil viscosity on the efficiency of oil displacement by alcohol has not previously been observed, probably because the range of viscosities used in earlier experiments was too restricted. It is the object of this paper to describe the relationships between the ternary phase diagram, fluid properties and the displacement achieved. A technique for controlling the nature of the displacement is also presented. THEORY AND DEFINITIONS PISTON-LIKE THEORY The theory of alcohol flooding has been discussed in some detail. SPEJ P. 37ˆ

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^

Solvent Flooding Displacement Efficiency in Relation to Ternary Phase Behavior

1972 ◽  
Vol 12 (02) ◽  
pp. 89-95 ◽  
Author(s):  
Ahmad H.M. Totonji ◽  
S.M. Farouq Ali
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Phase Behavior ◽  
Ternary Phase ◽  
Ternary Systems ◽  
Ternary Mixtures ◽  
Displacement Mechanism ◽  
Irreducible Water Saturation ◽  
Experimental Runs

Abstract The chief objective of the study was to exercise control on the system phase behavior through the use of mixtures of two alcohols exhibiting opposite phase behavior characteristics in the alcohol-hydrocarbon-water system involved. Such systems were employed in displacements in porous media to ascertain their effectiveness. Introduction Displacement of oil and water in a porous medium by a mutually miscible alcohol or other solvent has been the subject of numerous investigations. This process, in spite of its limited scope as an oil recovery method, has certain mechanistic features that are of value in gaining an understanding of some of the newer recovery techniques (e.g., the Maraflood* process). The works of Gatlin and Slobod, proposing piston-like displacement of oil and water by a miscible alcohol; of Taber et al., describing the displacement mechanism in terms of the ternary phase behavior involved; and of Holm and Csaszar, defining displacement mechanism in terms of phase velocity ratio, are major contributions in this area. In a later work, Taber and Meyer suggested the addition of small amounts of oil and water (as the case may be) to the alcohol used for displacement, since this helped to obtain piston-like displacements with systems that are usually characterized by the efficient displacement of either oil or water. APPARATUS, EXPERIMENTAL PROCEDURE, AND SIMULATOR PROCEDURE, AND SIMULATOR The procedure employed for determining the equilibrium phase behavior of ternary systems involved the titration of a hydrocarbon-water (or brine) mixture by the particular solvent (pure alcohol, or alcohol mixture) for the determination of the binodal curve, and the analysis by refractive index measurement of ternary mixtures having known compositions for the determination of the tie lines. Since the procedure is valid for strictly ternary systems, its use in this case where essentially quaternary systems are involved would yield the total alcohol content rather than the correct proportion of each alcohol. The ternary diagrams presented should be viewed with this limitation in mind. presented should be viewed with this limitation in mind. The apparatus used for experimental runs in porous media consisted of a positive displacement Ruska pump and a core encased in a steel pipe. Suitable sampling apparatus and auxiliary equipment were employed. Most runs consisted of injecting a slug of the particular solvent into a core initially containing a residual oil (waterflood) or irreducible water saturation, at a constant rate, and then following the slug by water or brine. The effluent samples collected were analyzed for the hydrocarbon, water and alcohol in order to plot the production histories. Complete experimental details and fluid production histories. Complete experimental details and fluid properties are given in Ref. 6. Table 1 lists the properties properties are given in Ref. 6. Table 1 lists the properties of the porous media used. Computer simulations of some of the experimental runs, as well as exploratory simulations, were carried out using the method earlier reported. The method basically consists in the representation of a porous medium by a certain number of cells containing immobile oil (or oleic) and water (or aqueous) fractions into which alcohol is injected in a stepwise manner allowing for phase changes. SPEJ P. 89

Development of the Surfactant-Based Chemical EOR Formula for Low Permeability Reservoirs

2021 ◽  
Author(s):  
Nancy Chun Zhou ◽  
Meng Lu ◽  
Fuchen Liu ◽  
Wenhong Li ◽  
Jianshen Li ◽  
...  
Keyword(s):  
Phase Behavior ◽  
Oil Recovery ◽  
Aqueous Solubility ◽  
Low Permeability ◽  
Chemical Flooding ◽  
Residual Oil ◽  
Key Factors ◽  
Low Salinity ◽  
Low Tension ◽  
Low Permeability Reservoirs

Abstract Based on the results of the foam flooding for our low permeability reservoirs, we have explored the possibility of using low interfacial tension (IFT) surfactants to improve oil recovery. The objective of this work is to develop a robust low-tension surfactant formula through lab experiments to investigate several key factors for surfactant-based chemical flooding. Microemulsion phase behavior and aqueous solubility experiments at reservoir temperature were performed to develop the surfactant formula. After reviewing surfactant processes in literature and evaluating over 200 formulas using commercially available surfactants, we found that we may have long ignored the challenges of achieving aqueous stability and optimal microemulsion phase behavior for surfactant formulations in low salinity environments. A surfactant formula with a low IFT does not always result in a good microemulsion phase behavior. Therefore, a novel synergistic blend with two surfactants in the formulation was developed with a cost-effective nonionic surfactant. The formula exhibits an increased aqueous solubility, a lower optimum salinity, and an ultra-low IFT in the range of 10-4 mN/m. There were challenges of using a spinning drop tensiometer to measure the IFT of the black crude oil and the injection water at reservoir conditions. We managed the process and studied the IFTs of formulas with good Winsor type III phase behavior results. Several microemulsion phase behavior test methods were investigated, and a practical and rapid test method is proposed to be used in the field under operational conditions. Reservoir core flooding experiments including SP (surfactant-polymer) and LTG (low-tension-gas) were conducted to evaluate the oil recovery. SP flooding with a selected polymer for mobility control and a co-solvent recovered 76% of the waterflood residual oil. Furthermore, 98% residual crude oil recovery was achieved by LTG flooding through using an additional foaming agent and nitrogen. These results demonstrate a favorable mobilization and displacement of the residual oil for low permeability reservoirs. In summary, microemulsion phase behavior and aqueous solubility tests were used to develop coreflood formulations for low salinity, low temperature conditions. The formulation achieved significant oil recovery for both SP flooding and LTG flooding. Key factors for the low-tension surfactant-based chemical flooding are good microemulsion phase behavior, a reasonably aqueous stability, and a decent low IFT.

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