Study on Reservoir Characteristics of the Fourth Member of Shahejie Formation in Zhanhua Sag, Jiyang Depression

The Huxiang carbonate rocks in the upper sub-member of the fourth member of the Shahejie Formation in the Zhanhua Sag are widely distributed, and the buried depth span is large. They have good exploration potential and can be used as important high-quality reservoirs. However, the horizontal and vertical changes of reservoirs are fast, the accumulation is complex, the difference of rock characteristics and the unclear distribution of favorable reservoirs in each facies zone limit the exploration and development of oil fields. Comprehensive utilization of casting thin sections, core physical properties, scanning electron microscopy, and other test analysis, the carbonate reservoir space structure, pore throat structure, and microscopic pore structure were systematically studied. The research shows that the Huxiang carbonate reservoir in the upper sub-member of the fourth member of the Shahejie Formation in the study area is dominated by limestone, which is a set of medium-low porosity-low permeability tight reservoir. The primary pores are basically not developed, and the reservoir space types are mainly fractures, intergranular pores, intergranular dissolved pores, and matrix pores. The porosity ranges from 0.4 % to 35.7 %, the average porosity is 7.41 %, and the permeability ranges from 0.100 mD to 597.000 mD, with an average permeability of 9.121 mD. The pore throat separation is good, mainly micro pore-micro throat.