Image-Based Pore Structure Characterization and Pore-Scale Fluid Flow Simulation of Fine-Grained Sandstones

The pore structure features are believed to determine the storage and seepage capacity of the reservoirs at various scales. Exploring fluid flow in tortuous pore systems is vital for the enhancement of oil and gas recovery. Image-based experiments were utilized here to explore the heterogeneous pore space at various scale. By combining the Volume of Fluid (VOF) model of finite volume method and adaptive polyhedron meshing technique, the simulation of oil-water two-phase flow at pore scale was realized, and the influence of pore structure on microscopic remaining oil was revealed. Due to the multi-type and multi-scale pore throats in low-permeability sandstones, the geometry and connectivity characteristics of pore space are strongly heterogeneous. The large pore throats significantly control the seepage capacity of sandstone, and constitute the undersurface dominant flow paths. The microscopic dominant water flow channels are generally developed in low-permeability sandstones, which are basically consistent with the dominant seepage channels of single-phase flow. The microscopic remaining oil of water-wet sandstones is dominated by pore-throat filling type, which is mainly distributed in medium and large pores. The formation of pore-throat filling remaining oil is mainly due to the “snap-off effect” in water-wet pores and the “passing-flow effect” caused by the heterogeneity of pore structure.