Micro-pore throat structure characteristics of ultralow permeability sandstone reservoir in Chang 8_2 reservoir of Zhanghan area,Qrdos Basin

The lithology of Chang 82 reservoir in Zhanghan area,Ordos basin is mainly of fine lithic arkose,low-porosity and ultra-low permeability.The reservoir pore types are various and mainly of primary intergranular pore,while because of the discrete distribution of pore size,smaller pore throat radius and strong heterogeneity,the oil producing capacity and oil displacement efficiency are poor and low.The poor reservoir physical property is the coefficient result of average throat radius,median pressure,driving pressure,partial degrees,the biggest mercury injection saturation and pore volume.According to the lithology,reservoir physical property parameters,micropore throat structure parameters and production capacity,Chang 82 reservoirs are classified into three types,among which type I and type II are optimized for late development.