苏里格气田召51井—统41井区储层成岩作用及致密性成因分析

Diagenesis of Sandstone and Genesis of Tight Reservoirs in Well Block Zhao 51-Tong 41of Sulige Gas Field,Ordos Basin

苏里格气田召51井—统41井区储层属于典型的致密储层。因此,搞清楚致密储层的成因、寻找有利储层是该区施行天然气有效勘探与开发亟待解决的主要问题之一。通过物源分析与岩心观察,并结合岩石薄片、阴极发光及扫描电镜等实验分析,认为研究区砂岩以低成熟度的岩屑砂岩和岩屑质石英砂岩为主。对储层孔隙结构进行分析,结果显示储层孔隙类型主要以晶间孔和粒内溶孔为主。研究区砂岩成岩作用主要有压实作用、胶结作用、溶蚀作用和交代作用,其中压实作用和胶结作用是形成致密性储层的主控因素。通过对研究区砂岩成岩相的分析,认为中等压实、高岭石充填、溶蚀相与中等压实、高岭石充填、方解石充填、溶蚀相是储层的主要成岩相。研究认为研究区储层致密的根本原因是其孔隙空间细小、连通性较差所致。

The reservoir in well block Zhao 51-Tong 41 of Sulige Gas Field is a Therefore,figuring out the genesis of tight reservoir, searching for the favorable typical reservoir. reservoir is one of the main problems for the natural gas exploration and development in this area. Through the analysis of prove- nance and core observation, combining with slice identification, casting slice, cathode luminescence and scanning electron microprobe studies,we reached the following conclusions：the main lithology of sandstone in this area is lithic sandstone and lithic silicarenite with low grade of maturity. The reservoir pore struc- tures are analyzed,and the results show the dominant types of pore are intergranular pore and intragrannu- lar dissolved pore. Diagenesis of sandstone in this area mainly includes compaction, cementation, corrosion and metasomatism, and the compaction and cementation are the main factors of tight reservoir. Based on the analysis of diagenetic facies, we found that moderate compaction-kaolinite filling-dissolution phase and moderate compaction-calcite filling-kaolinite filling-dissolution phase are the main ones. The conclusion is that small pore space and poor connectivity of pore are the underlying cause of tight reservoir in this study area.