鄂尔多斯盆地南缘中寒武统张夏组鲕粒滩相储层特征及主控因素

鄂尔多斯盆地寒武系深层具有良好的勘探潜力,中寒武统张夏组为寒武系勘探的重要目的层系。通过野外剖面详测和岩心、薄片观察及实验分析,对张夏组储层的特征、成因及主控因素进行了分析和研究,并预测了有利储层发育区。研究表明:①张夏组主要发育台缘鲕粒白云岩和台内鲕粒白云岩2类储层。②台缘带鲕粒滩累计厚度集中在50~300 m之间,鲕粒粒径平均为1.25 mm,鲕粒白云岩储集空间以溶蚀孔洞、粒间溶孔和晶间(溶)孔为主,平均测井孔隙度和渗透率分别为2.0%和0.038×10^-3μm²。③台内鲕粒滩厚度在50~120 m之间,鲕粒粒径平均为0.85 mm,鲕粒白云岩储集空间以溶蚀孔洞、粒间溶孔为主,平均测井孔隙度和渗透率分别为3.3%和2.787×10^-3μm²。④张夏组储层受鲕粒滩相、白云石化以及三级/四级层序界面控制,台缘规模有利储层发育在四级海退层序中上部的鲕粒白云岩地层中,台内规模有利储层发育在寒武系顶部不整合面之下的鲕粒白云岩地层中。预测台缘岐山—旬邑一带和台内陇东地区为两大规模有利储层发育区。

Characteristics of oolitic shoal reservoir and its main controlling factors of Zhangxia Formation in the southern margin of Ordos Basin

The Middle Cambrian Zhangxia Formation is an important target strata for Cambrian oil and gas exploration.Through detailed field outcrop survey,core and petrographic thin section observation and experimental analysis,the characteristics,genesis and main controlling factors of reservoir of Zhangxia Formation are analyzed and studied,and favorable reservoir development areas are predicted.The results show that:(1)Zhangxia Formation mainly develops two types of reservoirs:platform margin oolitic shoal dolomite and intra-platform oolitic shoal dolomite.(2)The cumulative thickness of oolitic shoal in platform margin zone is concentrated in 50~300 m,and the average diameter of oolitic is 1.25 mm.The reservoir space of oolitic dolomite in platform margin is dominated by dissolution pores,intergranular dissolution pores and intergranular(dissolution)pores,and the average logging porosity and permeability are 2.0%and 0.038×10^-3μm² respectively.(3)The thickness of intra-platform oolitic shoal ranges from 50 m to 120 m,and the average diameter of oolitic is 0.85 mm.The reservoir space of oolitic dolomite in the platform is dominated by dissolution pores and intergranular dissolution pores,and the average logging porosity and permeability are 3.3%and 2.787×10^-3μm² respectively.(4)The reservoir of Zhangxia Formation is controlled by oolitic shoal facies,dolomitization and third/fourth-order sequence boundary.The favorable reservoir of platform margin is developed in the oolitic dolomite strata in the middle and upper part of fourth-order regressive sequence,and the favorable reservoir of platform interior is developed in the oolitic dolomite strata below the unconformity surface at the top of Cambrian.On this basis,two largescale favorable reservoir development areas of Qishan-Xunyi area in platform margin and Longdong area in platform interior are predicted.