Pore structure characteristics of tight sandstone gas reservoirs, taking the Sulige area of Ordos Basin as an example

Taking the tight sandstone reservoir of the Sulige gas field in Ordos Basin as an example, the pore size distribution, pore morphology and pore type of the reservoir are revealed by a variety of comprehensive experimental analysis methods. The pore throat was distinguished by nuclear magnetic resonance, and the radius distribution of the pore throat was determined. A tight reservoir pore structure classification model is used to accurately classify pore structure types and evaluate reservoir seepage characteristics. The experimental results show that the pores in the study area are mainly secondary solution pores, hetero-basic pores, intergranular pores and micro-fractures. From the three-dimensional pore network, it is observed that the pore shape is mainly columnar and spherical, the distribution is not uniform, and there are many isolated pores in tight sandstone. The NMR T2 spectrum has bimodal characteristics, indicating that the aperture is mainly distributed in two ranges. A new pore structure classification parameter PSCI is determined by using the improved K-C equation. Using this classification model, the tight sandstone samples in the Sulige gas field are divided into four categories, and the pore relationships of various pore structures are obtained by fitting the pore relationship curves according to the categories, which is helpful to predict the permeability more accurately through the porosity.