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

鄂尔多斯盆地天环坳陷北部上古生界河8段砂岩储集层差异巨大，气水分布尤为复杂。本研究基于岩心数据、鉴定统计数据和各种薄层显微镜测量，利用扫描电子显微镜、荧光、拉曼光谱包裹体、相对磁导率分析和核磁共振。采集天环坳陷北部上古生界河8段样品，研究受差异成岩作用控制的储集层非均质性和气水分布特征。结果表明，压实和溶解是控制储层非均质性的两个最重要的因素。成岩-成藏序列和孔隙结构特征差异较大，影响储层润湿性、束缚水饱和度和驱气效率，从而控制气水分布。河8段为成藏致密气藏。根据成岩相与气水分布的关系，储层可分为三类。Ⅰ型压实作用弱，高岭石胶结沉积或蚀变，成岩相溶蚀作用强，孔隙度和渗透率高。该类型以粒模孔和粒间溶孔为主，产气量高。II型以中等强度压实、蚀变高岭石或绿泥石胶结为特征，成岩相溶蚀弱，孔隙度和渗透率中等。该类型以残留粒间孔、少量残留粒间孔和分散溶蚀孔为主，产气量低。Ⅲ型以中强压实、蚀变高岭石胶结、成岩相中强溶蚀为特征。该类型以高岭石晶间孔和分散溶蚀孔为主，形成高产水气藏。成岩相的中等强度溶蚀作用。该类型以高岭石晶间孔和分散溶蚀孔为主，形成高产水气藏。成岩相的中等强度溶蚀作用。该类型以高岭石晶间孔和分散溶蚀孔为主，形成高产水气藏。