Study on the Causes of Reservoir Differences in the Shan 1 Section and He 8 Section of the Su 75 Block in the Ordos Basin

为了进一步明确鄂尔多斯盆地苏75区块山1段和盒8段储层差异成因机理，以便指导该区域的下步稳产挖潜。通过对苏75区块山1段和盒8段储层的岩性、物性、沉积环境及成岩作用等因素的综合分析，结果发现：盒8段和山1段储层的岩石类型相似，均以长石石英砂岩和岩屑石英砂岩为主。但盒8段测试孔隙度主要分布在7%~10%的区域，山1段孔隙度主要分布在4%~10%。储层的储集空间以各类溶蚀孔隙为主，山1段各类溶蚀孔隙与盒8段存在明显的区别，碳酸盐岩溶孔在山1段为53.06%，在盒8段为33.13%；山1段的岩屑溶孔仅为0.08%远少于盒8段的17.77%。储层差异成岩作用密切相关，压实作用导致盒8段原生孔隙丧失率为9.5%~19.3%，导致山1段孔隙度损失率50%~63%，机械压实和粒间溶蚀作用对盒8段储层原生孔隙造成的损失率为50%~76%。胶结作用造成盒8段原生孔隙丧失率为9%~30%，造成山1段原生孔隙损失率为17%~32%。经研究认为，造成两段储层各方面差异的原因主要是两段沉积环境不同以及成岩作用产生的强度的不同。In order to further clarify the causes of the differences in the reservoirs of the Shan 1 and He 8 sections in the Su 75 block of the Ordos Basin, and to guide the next step of stable production and potential tapping in this area, a comprehensive analysis was conducted on the lithology, physical properties, sedimentary environment and diagenesis of the reservoirs in the Shan 1 and He 8 sections of the Su 75 block. The results show that the rock types of the He 8 and Shan 1 section reservoirs are similar, mainly consisting of feldspar quartz sandstone and lithic quartz sandstone. However, the porosity of the He 8 section is mainly distributed in the range of 7%~10%, while that of the Shan 1 section is mainly distributed in the range of 4%~10%. The reservoir storage space is mainly composed of various types of dissolution pores. There are obvious differences in various types of dissolution pores between the Shan 1 and He 8 sections. The carbonate dissolution pores in the Shan 1 section account for 53.06%, while in the He 8 section they account for 33.13%. The lithic dissolution pores in the Shan 1 section are only 0.08%, far less than 17.77% in the He 8 section. The diagenesis is closely related to the reservoir differences. Compaction causes a loss rate of primary porosity of 9.5%~19.3% in the He 8 section and 50%~63% in the Shan 1 section. Mechanical compaction and intergranular dissolution cause a loss rate of 50~76% of the primary porosity in the He 8 section. Cementation causes a loss rate of primary porosity of 9%~30% in the He 8 section and 17%~32% in the Shan 1 section. It is believed that the main reasons for the differences in various aspects of the two sections’ reservoirs are the different sedimentary environments and the different intensities of diagenesis.