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The Lower Shihezi Formation in the eastern part of Sulige gas field has high water content, where the exploitation of tight sandstone gas reservoir is considerably affected by the characteristics of fluid occurrence. Specifically, this study analyzed the porosity, permeability, lithology, pore throat heterogeneity and connectivity and their effects on fluid occurrenceby rock and ore identification, porosity and permeability analysis and NMR centrifugation. Results show that: ①the tight sandstone reservoir in the study area shows poor pore flow capacity, and bound water saturation. The flow capacity is closely related to the gas flow pressure difference (centrifugal force). ②Intercalations play a key role in controlling flow capacity. Abundant kaolinite content indicates that the reservoir has better connectivity, larger pore size and stronger overall pore water flow capacity. Illite has a strong water-holding capacity, which could easily cause capillary obstruction and limited flow capacity. ③The gas flow pressure difference (centrifugal force)is exponentially related to the pore diameter of reservoir pore water flow. ④The critical pore throat radius of the effective reservoir space is 0.089μm, and the mobile water saturation is 23.95% in Xiashihezi Formation in the eastern part of Sulige gas field.

Micro-pore structure affects the fluid storage and seepage in coal seams.In this paper, six samples from the Jurassic Yan'an Formation coal seam in the Shenmu area of the Ordos Basin were taken as the object of study.The pore distribution characteristics of coal seams were jointly characterized by NMR, CO2 adsorption and N2 adsorption at multiple scales, and the connectivity and homogeneity of microscopic pores were investigated by combining multi-scale joint characiterization with CT scanning.Results show that the micro-pores of coal are the main contributors to the specific surface area and pore volume, followed by meso-pores.There is a good uniformity in the pore size distribution of the micro-pores and meso-pores by combing NMR and adsorption, while considerable differences are found in the macro-pores.Displacement NMR and CT excel in reflecting the degree of connectivity, both of which are consistent in the characterization of connectivity.Parameters such as coordination number and seepage pore ratio can effectively reflect the degree of connectivity of the sample, whose patterns of connectivity is M6>M2>M12>M15>M10>M4.The saturation of bound water shows a satisfactory positive correlation with pore-throat ratio of coal samples.It can be seen that the pore structure has a great influence on the degree of fluid migration, which is the basis for studying and evaluating gas occurrence and seepage.