川东北地区上二叠统盘龙洞生物礁成岩作用研究

本文对宣汉盘龙洞上二叠统生物礁古油气藏成岩作用进行了详细的研究。其主要成岩作用类型有胶结作用、新生变形作用、白云岩化作用、去白云岩化作用以及压溶和溶解作用等。根据岩石中胶结物的胶结结构和矿物特征,初步判断该生物礁主要经历了海底成岩环境、大气淡水渗流潜流环境、海水与淡水混合带成岩环境和埋藏成岩环境。该区的白云岩主要是混合白云岩化形成的。值得强调的是,该区白云岩化作用和溶蚀作用对该生物礁岩石孔隙度的增加贡献很大,提供了良好的油气储集空间,这对恢复该生物礁储层孔隙发育历史,以及油气勘探和评价都有很重要的意义。

Diagenesis of the Upper Permian Panlongdong organic reefs in northeastern Sichuan

The diagenetic types of the Upper Permian Panlongdong organic reefs in northeastern Sichuan consist mainly of cementation, neomorphism, dolomitization, dedolomitization, pressolution and dissolution. The study of cementation textures and mineralogy of the cements shows that the diagenetic environments of organic reefs in the study area evolved from the submarine environment to the meteoric vadose and underflow environments to the mixed sea water-fresh water environment and finally to the burial diagenetic environment. The dolostones in the study area are originated from mixed dolomitization. The regional dolomitization and dissolution are demonstrated to make greater contributions to the increase in porosity and potential reservoir space for oil and gas accumulation, and thus have important significance for the oil and gas exploration and assessment.