Recuperación Mejorada De Crudo

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A Chemical Flooding Compositional Simulator
G. A. POPE R. C. NELSON
MEMBERS SPE.AIME

I

U. OF TEXAS AUSTIN SHELL DEVELOPMENT HOUSTON

CO.

ABSTRACT A one-dimensional: compositional, chemical-flood simulator was developed to calculate oil recovery as a function of several major process variables. The principal relationships included are phase behavior and interracial tensions as afunction oi and and sur/actant concentrations, electrolyte as a function of electrolyte and polymer viscosity polymer concentration. Emphasis was on studying the process itself, especially complex interactions that behavior, occur because 01 two- and three-phase flow, disp=sion, interiacicl tension, fractional exchange, chemical slug size, adsorption, cation and polymer transport. INTRODUCTIONNelson and Pope 1 reported laboratory flow results in which phase behavior plays a key role in oil recavery by chemical flooding. They show that many character sties of chemical floods can be explained by considering the equilibrium mixing and transport of surfactant/brine/oil systems in light of observed in external mixtures. phase behavior representations Although based on highly idealized of thekey properties involved, we believe that the simulator described here can yield significant insight into phase-related process mechanisms, among such as ‘toil swelling, ” the interactions process variables, and the relative merit of various chemical flooding strategies. The framework for systematically improving the compositional aspects of numerical simulation of chemical flooding is evident withour approach. This is because a completely compositional model based on total concentrations, rather than saturations, is assumed from the start. Then, the calculation of phase concentrations, and from them phase saturations, for any desired number of components and phases with any type phase behavior a relatively simpi e matter. is Conceptually, mathematically, and numerically, this approach isOriginal manuscript received in Society of Petroleum Engineers office Sept. 15, 1977. Paper accepted for publication May 20, 197S. Revised manuscript received Aug. 1, 1978. Paper (SPE 672s) first presented the SPE-AIME 52nd Annual Fall ‘i’ethnical Conference and Exhbition, held in Denver, Oct. 9-12, 1977. 0037-9999 /78/0010-6725 $00.2S @ 1978 Society of Petroleum Engineers of AIME OCTOBER, 1978simp’.. and easier to use than the traditional a~,(oach used in reservoir engineering simulation, a!though in principle they can be made equivalent. ‘.-he cases illustrated here are for up to six components and up to three phases, using highly representations of the binodal and simplified distribution curves for the surfactant/brine/oiI systems and the properties of the various phases that form.Even so, as many as 64 parameters are required to specify the process. Assumptions EQUATIONS, AND NUMERICAL TECHNIQUE The basic assumptions of the model are as follow. 1. The system is one-dimensional and homogeneous in permeability and porosity. exists equilibrium thermodynamic 2. Local everywhere. 3. The total mixture volume does not change when mixing individual components (AVM = O). 4. Gravityand capillary pressure are negligible. are a function of composition % Fluid properties only. 6. Darcy’s law applies. 7. Physical dispersion can be approximated adequately with numerical dispersion by selecting the appropriate grid size and time step. Additional assumptions are required to model such as interracial tension r various properties However, for the most part, these viscosity, etc. arechanged readily by the user and are not considered as basic as the above assumptions, but tidy with considerwhich also cm-i be re!axed, ably more effort. l%e auxiliary assumptions w;lI be examples with the specific givenr therefore discussed below. Given the above assumptions, the continuity i and np phase= are equations for each component

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