川东南六塘地区凉高山组致密砂岩成岩特征及差异成岩演化模式

Diagenesis characteristics and differential diagenetic evolution modes of Liangshan Formation tight sandstone in Liutang area,Southeast Sichuan

川东南地区下侏罗统凉高山组是致密砂岩油气勘探的新领域,但其储层非均质性强,有利储层特征及成岩演化规律等基础研究薄弱,制约了油气勘探开发。以川东南六塘地区凉高山组为研究对象,综合岩心、铸体薄片、扫描电镜和黏土矿物等资料,以岩石学、物性及成岩特征研究为基础,开展致密砂岩成岩相类型划分及差异成岩演化模式研究。结果表明:川东南六塘地区凉高山组储层以长石岩屑砂岩为主,储层物性致密,储集空间主要为残余原生粒间孔和粒间溶孔。储层发育压实、胶结和溶蚀等成岩作用,成岩阶段处于中成岩B期。储层主要发育强压实相、碳酸盐胶结相、溶蚀相和绿泥石膜胶结相4种成岩相类型。其中,强压实相砂岩粒度较细,塑性颗粒含量较多,物性致密;碳酸盐胶结相砂岩粒度较细,碳酸盐胶结物含量较高,物性致密;溶蚀相砂岩长石含量较高,溶蚀作用较强,储层物性相对较好;绿泥石膜胶结相砂岩颗粒较粗、绿泥石膜含量较高,压实中等,原生孔隙及溶蚀孔隙发育。绿泥石膜胶结相、溶蚀相砂岩为研究区2类有利储层。

Lianggaoshan Formation of Lower Jurassic in Southeast Sichuan is a new field of tight sandstone oil and gas exploration with great potential.However,its strong reservoir heterogeneity and weak basic research on favorable reservoir characteristics and diagenetic evolution laws restrict exploration and development.In this paper,the Lianggaoshan Formation in Liutang area of Southeast Sichuan was taken as the research object.The diagenetic facies were classified and diagenetic evolution model of tight sandstone was established based on the study of petrology,physical properties and diagenetic characteristics combined with integrating core,cast thin section,scanning electron microscope and clay minerals.The results show that the reservoirs of Lianggaoshan Formation in Southeast Sichuan are dominated by feldspathic lithic sandstone,the reservoir properties are tight,and the reservoir space is mainly residual primary intergranular pores and intergranular dissolved pores.Diagenesis such as compaction,cementation and dissolution is developed in the reservoir,and the diagenetic stage is the middle diagenetic stage B.The reservoir in the study area mainly develops four diagenetic facies:strong compaction diagenetic facies,carbonate cementation diagenetic facies,dissolution diagenetic facies and chlorite membrane cementation diagenetic facies.The sandstone with strong compaction diagenetic facies has fine grain size,high content of plastic particles and dense physical properties.The sandstone with carbonate cementation diagenetic facies has fine grain size,high content of carbonate cement and dense physical properties.The sandstone with dissolution diagenetic faces has high feldspar content,strong dissolution and relatively good reservoir physical properties.The sandstone with chlorite film cemented facies has coarse grains,high chlorite film content,medium compaction,primary pores and dissolution pores.In conclusion,the sandstone with chlorite mem‐brane cementation diagenetic facies and dissolution diagenetic facies are favorable reservoirs in the study area.