Structure of discontinuities in problems of oil displacement by reactants that influence the phase equilibrium

Abstract

In a large-scale description of oil displacement by chemical reactants, the distributions of the phase saturations and the concentrations of the components in the flow are discontinuous [i, 2]. Jumps correspond to narrow transitions regions, in which the changes in the variables are due to capillary, diffusion, and nonequilibrium effects. Investigation of these transition regions and the conditions of their existence makes it possible to establish the additional conditions that must be used to construct physically meaningful solutions in the large-scale approximation, i.e., when the indicated effects of dissipative nature are ignored. Processes of oil displacement by low-con-. centration reactants (solutions of an active additive) were analyzed in [I, 3]. Processes of oil displacement by concentrated reactants and reactants that influence the phase equilibrium differ in that the relative volumes of the phases change when there is interphase exchange of components besides changes in the relative mobilities. As a result, conditions arise under which there may be partial or complete mutual solubility of the phases. At the same time, the number of phases and the part they play in the flow can change during the displacement process; this leads to a number of dis~inctive hydrodynamic phenomena and to an extension in the variety of basic solutions to the problem of frontal displacement [4].