四川盆地侏罗系凉高山组岩相、岩相组合及其与油气的关系OA

In order to clarify the lithofacies types,source rock conditions,and reservoir properties,identify the dominant lithofacies associations of the Lower Jurassic Lianggaoshan Formation in the Sichuan Basin,a comprehensive evaluation was conducted on lithofacies,lithofacies associations and their relationships with hydrocarbon generation and accumulation,through analyses of petrology,geochemistry and reservoir physical properties using field outcrop sections and drilling core data.The following results are obtained.(i)There develops six lithofacies types in the Lianggaoshan Formation of this basin:sandstone(Type A),siltstone(Type B),massive shale(Type C),laminated shale(Type D),(thin)interbedded sandstone-mudstone(Type E),and mudstone(Type F).(ii)On the basis of lithofacies classification above,five types of lithofacies associations are identified as:sandstone+massive shale(TypeⅠ),sandstone+mudstone(TypeⅡ),sandstone+siltstone(TypeⅢ),(thin)interbedded sandstone-mudstone+laminated shale(TypeⅣ),and laminated shale+massive shale(TypeⅤ).(iii)The Lianggaoshan Formation shales exhibit the average total organic carbon(TOC)of 1.55%and the average hydrocarbon generation potential(S1+S2)of 2.21 mg/g.Specifically,Types C and D reflect good source rock conditions,while Type E shows relatively poor ones.(iv)Lithofacies types vary significantly in reservoir properties,with the average porosities of 5.30%,1.44%,3.42%,3.24%,and 2.22%for Types A,B,C,D,and E,respectively.It is evident that Types A exhibits notably higher porosity than the other lithofacies,followed by Types C and D,then Type E,while Type B shows the lowest porosity.(v)Comprehensive analysis on lithofacies associations demonstrates that TypeⅠ has the best source rock and reservoir conditions,indicating the optimal association.Meanwhile,TypesⅣ andⅤ are both favorable ones.It is concluded that the Lianggaoshan Formation in the Sichuan Basin has a promising potential,and the clarification of dominant lithofacies associations provides a theoretical support for shale oil and gas exploration and development.