Experimental Study on Microscopic Water Flooding Mechanism of High-Porosity, High-Permeability, Medium-High-Viscosity Oil Reservoir

Abstract

After the development of high-porosity, high-permeability, medium-high-viscosity oil reservoirs enters the high-water-cut stage, the remaining oil is highly dispersed on the microscopic scale, which leads to a change in the oil-water-flow law. If the enrichment and mobilization laws of the microscopic remaining oil cannot be truly and objectively described, it will ultimately affect the production of oil fields. At present, few studies have directly revealed the microscopic water flooding mechanism of high-porosity, high-permeability, medium-high-viscosity oil reservoirs and the main controlling factors affecting the formation of remaining oil. Starting with micro-physical simulation, this study explores the water flooding mechanism on the microscale, the type of remaining oil and its evolution law, and analyzes the main controlling factors of different types of remaining oil so as to propose effective adjustment and development plans for different types of remaining oil. It is found that this type of reservoir has a serious jet filtration phenomenon in the early stages of water flooding and is accompanied by the penetration of injected water, detouring flow, pore wall pressing flow, the stripping effect, and the blocking effect of the rock skeleton. The remaining oil is divided into five types: contiguous flake shape, porous shape, membrane shape, striped shape, and drip shape. Among them, the transformation of flake-shape and porous-shape remaining oil is greatly affected by the viscosity of crude oil. The decrease effect of crude oil viscosity on contiguous residual oil was as high as 33.7%, and the contiguous residual oil was mainly transformed into porous residual oil. The development of membrane-shape, striped-shape, and drip-shape remaining oil is more affected by water injection intensity. The decrease in water injection intensity on membrane residual oil was as high as 33.3%, and the membrane residual oil shifted to striped and drip residual oil. This paper classifies remaining oil on the microscopic scale and clarifies the microscopic water flooding mechanism, microscopic remaining oil evolution rules, and the main controlling factors of different types of remaining oil in high-porosity, high-permeability, medium-high-viscosity oil reservoirs.