An Analytical Model for One-Dimensional, Three-Component Condensing and Vaporizing Gas Drives

Abstract

Abstract An analytical model based on the method of characteristics is presented for the calculation of onedimensional (1D), three-component condensing and vaporizing gas drives. The model describes (1) mass transfer between oil and gas, (2) swelling and shrinkage, (3) viscosity and density changes, (4) gravity stabilization, and (5) rock/fluid interaction. The main assumptions of the model are local thermodynamic equilibrium and the absence of dispersion, diffusion, and capillarity. Example calculations are presented that bring out the main features of both condensing and vaporizing gas drives and also indicate the importance of mass transfer between the phases. In the special case of "developed miscibility," the model predicts a piston-like displacement having a complete recovery at gas breakthrough. The main applications of the model are in (1) conceptual studies of gas drives in which mass transfer plays an important role and (2) the calibration and checking of numerical reservoir simulators for multicomponent, multiphase flow.