A New Description of Multi-phase Flow Behavior at Boundary Layers of Low-permeability Porous Media

Abstract

At present, the recovery factor of low permeability oilfield in China is only about 20%, which is enormously lower than the recovery factor index of 60% by using water-chemical flooding in medium and high permeability layer. There are a lot of causes that resulted in low recovery factor, among them that the complex pore structure, tiny throat, large pore throat ratio and non-Darcy flow in low-permeability oil layer are the main causes that restrict the low-permeability oil layer to enhance the recovery factor. Based on the research results about micro-fluid flow and non-Darcy flow, microflow of water drive and micro-acting force in the porous media are researched in this paper, establishing the expression of fluid viscosity factor, 2D flowing control equation and the relevant boundary condition under the conditions of liquid/solid interaction in the micro-pore media, all that gain the flowing rules of fluid under these two conditions of considering L/S interaction or not considering that. Numerical calculation shows that under the condition of L/S interaction, the radial velocity distribution near the solid wall changes obviously, and the curve form changes from convex to concave. The tinier the capillary radius, the stronger the L/S interaction is. The larger n value is, more obvious the flowing velocity decrease in the boundary layer. The results will help people dealing with improving recovery factor of low permeability reservoir, and understanding the fluid behavior in vessel.

Keywords: low-permeability; micro-acting force; boundary layer; numerical simulation; pore structure; micro-flow PACS: 47.55.Mh, 47.50.+d, 34.20.Gj