Microscopic distribution of fluid in Sulige tight sandstone gas reservoir and its influencing factors

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.