鄂尔多斯盆地中东部致密砂岩储层地质特征及控制因素

Geologic characteristics and controlling factors of tight sand reservoir in the mid-eastern Ordos Basin

鄂尔多斯盆地中东部二叠系致密砂岩储层地质特征和储层控制因素研究尚属空白。在岩心描述、分析化验和成岩演化分析等基础上,对该储层的微观特征进行了系统描述,并对其控制因素进行了研究。结果表明,盒8段和山2段储层毛管压力曲线为陡斜式,孔、渗条件较差,平均孔隙度分别为6.14%和4.49%,平均渗透率分别为0.389 mD和0.749 mD,属致密砂岩储层。受沉积环境和成岩作用的控制,盒8段和山2段储层主要发育于水下分流河道微相中,且普遍进入晚成岩阶段B亚期,部分地区山2段储层甚至进入晚成岩阶段C亚期。压实作用及硅质、碳酸盐和黏土胶结作用使储层物性变差,溶蚀作用改善了储层的孔、渗条件,使储层物性变好。

The study on the geologic characteristics and controlling factors of Permian tight sand reservoir in the mid- eastern Ordos Basin is still a blank field. Based on core description, rock sample analysis and test, and diagenetic evolution analysis, this paper studied the microscopic characteristics and controlling factors of the reservoir. The results show that the capillary pressure curves in the eighth member of Shihezi Formation and the second member of Shanxi Formation are characterized by steep tilt, which indicates poor porosity （the average value of the two members is 6.14% and 4.49% respectively） and permeability（the average value of the two members is 0.389 mD and 0.749 mD respectively）. The reservoir development is controlled by depositional settings and diagenesis. The reservoirs of the eighth member of Shihezi Formation and the second member of Shanxi Formation are mainly developed in distributary channel sand bodies of the delta front subfacies and in the late diagenetic stage B, and the second member of Shanxi Formation is even in the stage C in some region. The compaction and cementation of silica, carbonate and clay mineral make the reservoir properties poor, and dissolution is constructive for reservoir properties.