THEORY OF MULTICOMPONENT GAS OIL DISPLACEMENTS

Chromatographic separations that occur during two-phase flow in a poro us medium are analyzed for one-dimensional, dispersion-free displaceme nt of a liquid hydrocarbon mixture (oil) by a vapor phase mixture (gas ). We show that displacement behavior is controlled by a set of key eq uilibrium tie lines, all of which are determined by geometric construc tions in composition space: two of the key tie lines are those that ex tend through the initial oil and injection gas compositions, and the r emainder are tie lines that are located at intersections of ruled surf aces of tie lines. Very efficient displacement of oil by gas results i f any of the key tie lines is a critical tie line. That high displacem ent efficiency is the basis of so-called miscible gas injection proces ses for enhanced oil recovery.