Pore scale investigation on scaling-up micro-macro capillary number and wettability on trapping and mobilization of residual fluid.


School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, Sichuan, People's Republic of China. Electronic address: [Email]


The mobilization mechanism of the trapped phases controlled by the viscous force and capillary force in porous media is crucial to various engineering applications. In this paper, pore scale water flooding process in rock models with nonuniform wettability is simulated by computational fluid dynamics (CFD) using the volume of fluid (VOF) model. Four types of rock are imaged by micro-CT (μ-CT) and adopted as inputs to generate the structured mesh models. The simulations of two-phase flow are carried out to study the immiscible displacement process in the development of oil fields. The scaling-up critical capillary number at micro-macro scale are acquired and validated, the effects of which on relative permeability, residual oil recovery and immiscible displacement efficiency are analyzed. The simulation results indicate that the critical capillary number at microscopic scale ranges from 10-6 to 10-5 for water-wetted and oil-wetted rock respectively, and approaches to 1 at the macro scale. The effect of wettability on oil recovery is positive for intermediate-wetted or weak water-wetted rock, while negative for strong wettability.


Capillary number,Micro-CT,Nonuniform wettability,Pore-scale modeling,Relative permeability,