塔里木盆地塔中-巴楚地区志留系柯坪塔格组成岩作用及成岩相

Diagenesis and Diagenetic Facies of Kepingtage Formation of the Silurian in Tazhong-Bachu Area of Tarim Basin

塔中-巴楚地区志留系柯坪塔格组是塔里木盆地重要的勘探目的层之一。在对该区柯坪塔格组沉积背景认识的基础上,通过铸体薄片、扫描电镜、电子探针及X射线衍射等分析方法对储层成岩作用进行了系统的研究,认为研究区砂岩主要经历了压实-压溶作用、胶结作用、溶解作用,目前已达到了晚成岩A期的末期。塔中地区与巴楚地区柯坪塔格组成岩作用的差异主要是原始沉积环境导致的物质成分差异所致,并最终导致了物性的差异。依据成岩作用对物性的影响,划分出4种成岩相,其中早期碳酸盐胶结物强溶解与晚期弱-中等充填成岩相为最有利储集相带,强石英次生加大成岩相、碳酸盐强烈胶结成岩相和强烈压实成岩相不利于孔隙的发育。

Kepingtage Formation of the Silurian in Tazhong-Bachu Area of Tarim Basin was one of the main target zones for oil exploration in Tarim Basin.Based on the recognition of depositional environment in Kepingtage Formation of the Silurian in Tazhong-Bachu Area,various methods,such as cast thin section,scanning electron microscope,electronic probe and X-ray diffraction were used to systematically and thoroughly study the diagenesis in the area.It was considered that sandstone in the area went through the diagnesis stage of compaction,pressure-solution,cementation and solution,and currently it was at the telophase of late diagenesis stage of Period A.The differences of diagenesis between Tazhong Area and Bachu Area were mainly due to the component differences form the original depositional environment,and it finally led to the differences of porosity and permeability.According to the influence of diagenesis on porosity and permeability,it is divided into 4 types of diagenetic facies,in which the strong dissolution of early carbonate cementation and medium to weak of later cementation diagenetic facies are the most favorable reservoir facies,while the strong quartz cementation ciagenetic facies,the strong carbonate cementation diagenetic facies and the strong compaction diagenetic facies are unfavorable for pores development.