Pore Structure and Permeability Characterization of Tight Sandstone Reservoirs: From a Multiscale Perspective

Abstract

Due to the influence of a sedimentary environment, sandstone characteristics, diagenesis, and geological structure, the complexity and heterogeneity of the pore structure in tight sandstone reservoirs act as key barriers for accurate characterization of the influence of different pore microparameters on reservoir physical properties. This paper obtained different scale microscopic pore–throat parameters through mercury intrusion porosimetry (MIP) and digital core reconstruction models. According to the connectivity of different scale pores, connected pore structure parameters, and pore fractal dimension, the pore structure characteristics of tight sandstone reservoirs were evaluated. Subsequently, through partial correlation analysis, the contribution rate of different scale connected pore parameters to permeability and porosity was clarified. Then, a multiparameter fitting equation for the absolute permeability and porosity of the rock was obtained through multiple regression analysis. The analysis results show that (1) the connected pores of tight sandstone reservoirs are mainly mesopores, with the pore radius distribution between 1 and 3 μm, and throat radius distribution between 0 and 2 μm. (2) The complexity of the pore structure in tight sandstone reservoirs is most strongly correlated with the fractal dimension of the pore structure at the mesoporous scale. (3) The pore radius and throat length at the mesoporous scale have the strongest correlation with the absolute permeability of the rock, and the pore radius at the mesoporous scale has the strongest correlation with the porosity of the rock. (4) The multiparameter fitting equation established by multiple regression analysis quantitatively and qualitatively analyzed the impact of microscopic parameters of the pore–throat structure at different scales on reservoir properties, achieving the purpose of predicting the absolute permeability and porosity of the tight sandstone reservoir. It provides guidance for the study of the pore structure and permeability characteristics of tight sandstones.