Effect of Viscous Crossflow on Miscibility Development in a Two-Layer Flow System: Part I - Ternary Vaporizing Gas Drives

Abstract

SUMMARY This paper examines the effect of permeability heterogeneity and viscous crossflow on ternary vaporizing gas drive displacements. Material balance equations that describe multicomponent, multiphase flow in a two-layer system are solved by finite differences for the case of maximum (vertical equilibrium) viscous crossflow between layers. The effects of interlayer permeability ratio and operating pressure on composition paths, composition and saturation profiles, and oil recovery are reported. Fluid mixing due to viscous crossflow is shown to cause significant amounts of two-phase flow in displacements that would be multicontact miscible in the absence of crossflow. Although the induced two-phase flow reduces local displacement efficiency, viscous crossflow improves overall recovery because a decrease in mobility contrast between layers reduces channeling, and because some oil is moved from the low permeability layer to that with faster flow.