Characterization of Pore Structure and Oil-Water Two-Phase Seepage Properties in Sandstone Reservoirs

Abstract

In this study, the pore structure and oil-water phase seepage characteristics of sandstone reservoirs of the Yanchang Formation in the Ordos Basin were deeply analyzed. Through scanning electron microscopy observation, oil-water phase percolation experiments and nuclear magnetic resonance (NMR) experiments on 30 core samples, the pore structure was categorized into uniform macroporous, striated, microfractured and dense types. The experimental results show that the uniform macroporous type pore structure shows the strongest seepage capacity, and its ratio of liquid-measured to gas-measured permeability is 0.724 on average, while the dense type pore structure has the weakest seepage capacity, and the ratio is 0.091 on average; NMR T2 spectral analysis reveals that the cores with different types of pore structure show significant characteristic differences in the water-driven oil drive process, especially in the substitution of oil in the macroporous and micrometer pore In particular, the oil substitution in large pores and micron pores is remarkable, that is, the oil-water seepage process and the response of seepage and suction of cores with different types of pore structure are obviously different, which is a better way to study the characteristics of oil-water seepage and distribution of oil and water; the uniform macroporous type and the striptype pore structure are more effective in oil-water two-phase seepage, and the microfracture type and the dense type are relatively poor. This paper provides a basis for the exploitation of tight reservoirs in the study area, which is of great theoretical and practical significance for optimizing the oilfield development strategy and improving the efficiency of oil and gas exploitation.