Analysis of Microscopic Displacement Mechanisms of Dilute Surfactant Flooding in Oil-wet and Water-wet Porous Media

In all the enhanced oil recovery processes, flow of displacing and displaced fluids on a microscopic scale in a petroleum reservoir rock is affected by the wettability of the reservoir rock. Gaining proper knowledge of the dominant microscale multiphase flow mechanisms enables us to better predict the foremost prevailing macroscale flow behavior of the process. This research provides new insights into the effect of wettability on microscopic two-phase flow displacement mechanisms of dilute surfactant flooding using micromodel. It was inferred that the primary mechanisms of dilute surfactant flooding in the oil-wet medium were, intra-pore and inter-pore bridging of the surfactant solution, pore wall transportation of the oleic phase, formation of water-in-oil macroemulsion, and formation of partially continuous surfactant solution which enhanced the oil recovery. In water-wet medium, transportation of oil phase along pore body and neck walls, complete and incomplete inter-pore bridging, and deformation and stringing of the residual oil were the primary mechanisms of dilute surfactant flooding which made the residual oil entrapped in micromodel easily move forward and enhance oil recovery.