The Development Model Of Shale And The Conditions Of Shale Gas Accumulation In Lower Jurassic Ziliujing Formation In Northeastern Sichuan Basin

Having huge potential of exploration and development,the continental shale gas resource is rich in Northeast Sichuan Basin.The Shale in Lower Jurassic Ziliujing Formation is the main target stratum,shale gas exploration has good advantages for shale gas accumulation.However,the current study was primary.Especially,the development model of the continental shale was not established,the conditions of shale gas accumulation was not clear.Integrating core,field outcrop,logging,seismic and organic geochemistry data,using the theory of geology,this paper find out the characteristics of sequence and sedimentary and the conditions of shale gas accumulation in Ziliujing Formation,establish development model of continental shale,and get the following conclusions:?1?By various sequence interface,the Ziliujing Formation in Northeast Sichuan Basin can be divided into two third-order sequences?SQ1 and SQ2?,who consist of a PST and a RST.The largest transgression surface developed on the top of the PST of SQ1 and SQ2 is the most favorable development part of the continental shale.?2?The shale of the Ziliujing Formation in northeastern Sichuan Basin are mainly developed in the lake depositional system.From north to south,the sedimentary water becomes deeper,and the transition from shoreland,shallow lake to semi deep lake occurs.The Da'anzhai member is more extensive than the Dongyuemiao member,and the shallow lakes are more developed.In the early middle period of the Da'anzhai member,the semi deep lake mud near the center of the lake basin is the most favorable sedimentary microfacies for the development of continental shale.?3?The lower Jurassic in the northeastern Sichuan Basin has favorable conditions of continental shale gas accumulation.The abundance of organic matter is high,the organic type is mainly II₁,and the thermal maturity of organic matter is moderate.The accumulated thickness of shale is large.Mineral composition is mainly composed of quartz and clay minerals.Shale properties are generally good,mainly controlled by sedimentary microfacies.?4?Based on the development of continental shale,sedimentary facies and abundance of organic matter,Continental shale development model are established.There are three types of rich continental shale,organic-rich continental shale,organic-medium continental shale and organic-poor continental shale.