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歧口凹陷沙河街组一段下亚段湖相碳酸盐岩储层储集空间多样、物性变化快、非均质性极强,其储层质量的差异性严重影响了该区油藏分布规律的认识和有利储层的预测。针对这一问题,综合利用钻井资料、测井资料、岩心观察、薄片鉴定及分析化验等资料对研究区储层特征及储层质量差异机理进行了研究。研究发现,沙一下亚段碳酸盐岩储层储集空间包括原生孔隙、次生溶孔和裂缝,为中孔中渗储层。储层质量差异具体表现为储层的孔渗性在空间上差异明显;优势储集空间具有明显的分区性;不同类型的碳酸盐岩物性差异很大,颗粒石灰岩的孔渗性最好,泥粉晶白云岩次之,灰泥石灰岩最差。储层质量差异受沉积相、不均匀溶蚀和构造作用的控制。生物滩、鲕粒滩是优质储层发育的有利沉积相带;断层附近的泥粉晶白云岩有利于裂缝发育。由岩石矿物成分、原生孔隙及裂缝发育程度的不同引起的不均匀溶蚀是导致研究区碳酸盐岩储层质量差异的根本原因。
The reservoirs of lacustrine carbonate reservoirs in the lower section of the Shahejie Formation in the Qikou Depression are diverse in reservoir space with rapid changes in physical properties and strong heterogeneity. The differences in reservoir quality have seriously affected the reservoir distribution Understanding and favorable reservoir prediction. In response to this problem, the reservoir characteristics and the mechanism of reservoir quality differences in the study area are studied comprehensively by using well data such as drilling data, well logging data, core observation, slice identification and analytical laboratory data. It is found that the reservoir space of the sub-subsurface carbonate reservoir consists of primary pores, secondary pores and cracks, and is a medium-permeability reservoir. The difference of reservoir quality is manifested in that the porosity and permeability of the reservoir are obviously different in space; the dominant reservoir space is obviously divided; the physical properties of different types of carbonate rocks are quite different; the porosity and permeability of granular limestone are the best, Mud powder dolomite followed, stucco limestone worst. The differences in reservoir quality are controlled by sedimentary facies, uneven dissolution and tectonism. Biotan and oolitic beaches are favorable sedimentary facies for the development of high-quality reservoirs; muddy dolomite near the fault is favorable for fracture development. Uneven erosion caused by the difference of rock mineral composition, primary porosity and fracture development is the fundamental reason for the difference in carbonate reservoir quality in the study area.