A New Micellar Phase-Behavior Model for Simulating Systems With Up to Three Amphiphilic Species
- L.P. Prouvost (U. of Texas) | T. Satoh (U. of Texas) | K. Sepehrnoori (U. of Texas) | G.A. Pope (U. of Texas)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 16-19 September, Houston, Texas
- Publication Date
- Document Type
- Conference Paper
- 1984. Society of Petroleum Engineers
- 4.3.4 Scale, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.2.1 Phase Behavior and PVT Measurements, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.5.1 Simulator Development, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating
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A thermodynamic model has been developed for the phase behavior of micellar systems containing up to phase behavior of micellar systems containing up to three amphiphilic species. This model has been tested against experimental data using chemicals typical of those used in surfactant flooding. A fairly good match of static phase behavior experiments has been obtained. The model has been implemented in a compositional simulator and found to be both simple enough and accurate enough for practical reservoir engineering calculations. One important design is to study the separation of the chemicals as they transport through the reservoir. This type of study should be useful in selecting surfactants and cosurfactants for optimal behavior. Relatively little experimental phase behavior data are needed to estimate the parameters in the model .
The phase behavior of multicomponent systems used in chemically enhanced oil recovery has been extensively studied for some years because it has been proven to be one of the key-factors in the success or proven to be one of the key-factors in the success or the failure of the recovery process. In fact, many other physical properties, such as phase viscosities, relative permeabilities, interfacial tensions and surfactant adsorption depend on phase compositions and saturations.
The micellar/polymer process involves mixtures of a large number of chemical species and the phase behavior of such systems is difficult to handle. In most cases, water, electrolytes, oil, surfactant and cosurfactant are present. A general trend today is to design alcohol-free micellar processes by tailoring the surfactant molecule in order to prevent undesirable phase behavior (liquid crystal regime or other condensed phases). Though achievement of this goal is highly desirable, since it cancels the problem of differential transport of surfactant and problem of differential transport of surfactant and cosurfactant in the reservoir, it is not always possible to completely avoid the presence of alcohol or possible to completely avoid the presence of alcohol or other cosurfactant, especially in very low temperature reservoirs. Besides, in some cases, even cosurfactants are used, or the surfactant is made of various species which do not behave collectively and so partition selectively. So, the number of chemical species to be considered is at least four, namely brine, oil, cosurfactant and surfactant, or five if two cosurfactants are used or if the surfactant has to be considered as two species of different HLB. Salt and water will be taken as one brine pseudocomponent. pseudocomponent. The phase behavior of four-component systems has been represented in the past on ternary planes, for example by lumping together two of the components in a fixed ratio. The most common lumping for simulation purposes is surfactant and cosurfactant referred to as chemical or active mixture. This way of representing phase behavior leads to some inconsistencies, since there is no reason why surfactant and cosurfactant, especially alcohol, should partition collectively, and in fact there is strong partition collectively, and in fact there is strong evidence they do not. When lumping together surfactant and alcohol, middle-phase points are no longer unique and optimal salinity changes with overall concentration. Other kinds of ternary planes have been used (fixed surfactant to hydrocarbon, ... ), but once again, they only enable representation of binodal surfaces and not tie-lines or tie-triangles, since phase compositions do not lie in the same triangles as the overall composition points. points. Therefore, the phase behavior of such systems has to be represented on three-dimensional tetrahedric diagrams. In this paper, what we try to achieve first, is to define pseudoternary planes, i.e. slices through the tetrahedron, so that when phase behavior is studied in these planes, any phase separation which might occur, yields phase compositions lying in the same plane as overall composition points (Figure 1). Obviously, this issue is closely points (Figure 1). Obviously, this issue is closely related to the one of alcohol partitioning between the phases and we make use of a thermodynamic model for alcohol partitioning, referred to as the pseudophase model , which has been developed by Biais et pseudophase model , which has been developed by Biais et al.
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