Diagenetic features and porosity dense evolution of Chang 8 tight sandstone reservoir in Hujianshan area, Ordos Basin

Abstract Diagenesis is the main reason for tight reservoir lithology, complex pore-throat structure, strong heterogeneity, and variable occurrence distribution characteristics of fluid in pore-throat, which directly restricts Chang 8 oil layer group Ordos Basin. Exploration development. Based on analysis a large number cores thin slices, through application scanning electron microscopy, high-pressure mercury intrusion other experimental testing methods, diagenesis Hujianshan area Basin mechanism process porosity evolution are analyzed depth. The relationship between different diagenetic facies belts, pore structures their impact quality further explored. results show that mid-diagenetic stage A, mainly experienced compaction-pressure dissolution, cementation, dissolution diagenesis. compaction caused loss primary pores sandstone, most important factor densification study area, followed by cementation carbonate clay minerals. chlorite film formed early retained particles. inter-pores maintain good physical properties, affected acidic environment. unstable feldspar minerals dissolve. produced effectively improve connectivity permeability pores. reduces average 19.37% rate reaches 51.86%. 11.97% 32.66%. increases 3.26% average. In evolution, A authigenic middle reasons substantial decrease porosity. B due to its short duration. Less lost. secondary generated basically filled with microcrystalline calcite, while organic acid limited. According characteristics, combined logging response whole divided into four facies. Among them, residual chlorite-membrane intergranular-pore favorable findings this can help better understanding quantitative pores, reveal diagenetic-pore rules sandstone reservoirs provide basis evaluation prediction area.