New analytical solutions for 1-D multicomponent gas injection problems

Abstract

Analytical models for 1-D displacement of oil by gas have been developed during the last 15 years. It was observed from semi-analytical and numerical experiments that several thermodynamic features of the process (MMP, key tie lines, etc) are not dependent on transport properties. After change of independent variables, the compositional (n-1)*(n-1) model for n-component flow is divided into a thermodynamics auxiliary (n-2)*(n-2) system and one transport equation. Explicit projection and lifting procedures are derived. The new technique developed permits splitting for both self-similar continuous injection problems and for non-self-similar slug injection problems. New different solutions for non-self-similar problems of gas injection in oil reservoirs are presented. With respect to 3-D flows, splitting takes place only for the case of constant total mobility (where the stream line concept is valid). For the general case of the total mobility variation, mixing between fluids that enter different streamlines occurs, and splitting does not happen any more.