Control of differential diagenesis of tight sandstone reservoirs on the gas–water distribution: A case study on the Upper Paleozoic He 8 Member in the northern Tianhuan depression of the Ordos Basin

The sandstone reservoirs in the Upper Paleozoic He 8 Member northern Tianhuan depression of Ordos Basin are vastly different and feature particularly complex gas–water distributions. Scanning electron microscopy, fluorescence, Raman spectroscopy inclusions, relative permeability analysis, nuclear magnetic resonance were utilized this study based on core data, identification statistics, various thin-section microscope measurements. Samples from collected to characteristics reservoir heterogeneity distribution, which controlled by differential diagenesis. results indicate that compaction dissolution two most important factors controlling heterogeneity. Large differences diagenesis–accumulation sequences pore structure affect wettability, irreducible water saturation, gas displacement efficiency, thereby distribution. is a densified because accumulation. Reservoirs can be divided into three types relationship between diagenetic facies Type I characterized weak compaction, precipitate or altered kaolinite cementation, strong facies, high porosity permeability. This type dominated grain-mold pores intergranular produces with yield. II medium-strength chlorite medium residual pores, few dispersed producing low III facies. intercrystal