Study On The Potential Exploration Target Layer Of Carboniferous Shale Gas In Guizhong Depression

With the change of China's energy structure from conventional oil and gas to unconventional oil and gas,the emergence of shale gas just fills the awkward situation of China's single energy model.The development of marine shale in the south of China makes China shift its focus to the study of marine shale and make a significant shale gas breakthrough in the Sichuan basin,in this background,many scholars start to conduct Guangxi area in order to find more shale gas resources.In this context,many scholars started to study the Guangxi area in order to find more shale gas resources.Many studies mainly focus on the Devonian mud shales,but the carboniferous has become a forgotten field of shale gas research,so it is especially important to supplement the information on the carboniferous in the Guangxi area.This study investigates and analyses the Carboniferous mud shale layers in ten outcrop sections in the Guizhong Depression through outcrop stratigraphic methods,observational studies of key outcrop sections in the field,collection of mud shale samples from key sections and determination of organic geochemical parameters(TOC and Ro),including the delineation of Carboniferous stratigraphy,deposition and spreading characteristics of Carboniferous mud shale,organic geochemical characteristics of mud shale and prediction of potential exploration target layers.Firstly,the stratigraphic stratigraphy of the Carboniferous is divided through field outcrops,and the deposition(sedimentary facies type)and spreading characteristics of the mud shale layer(vertical and horizontal distribution)are studied in conjunction with the stratigraphic stratigraphy,and then the organic geochemical analysis data of the mud shale layer are used to predict potential exploration targets.It has been studied that six depositional sequences are delineated in the Carboniferous of the Guizhong Depression,of which the sixth depositional sequences is composed of the bottom strata of the Lower Permian and the top strata of the Upper Carboniferous.The observed mud shale layers are mainly located in the transgression system tract and the condensed unit of the depositional sequence.Along the ZiyunLuodian-Nandan-Du'an fault zone around and eastward of the Yizhou fault zone are distributed basinal facies mud shale layers(around Nandan-Hechi-Yizhou-Luzhai),around the basinal facies are distributed mud shale layers(around Huanjiang-Lucheng),and on the northward continuous land terrace are distributed marine marsh facies mud shale layers(around Shangchao townLucheng county-Huangjin town).The thickness of mud shales in the Luzhai Formation ranges from 100 m to 350 m,with a maximum thickness of 600 m in the Luzhai area;the thickness of mud shales in the Yingtang Formation ranges from 160 m to 180m;the thickness of mud shales in the Golden Formation is about 35 m to 65m;the thickness of mud shales in the Simen Formation is135m;and the thickness of mud shales in the Luocheng Formation is 160 m.By combining the summary of previous shale gas exploration criteria and predicting the potential exploration targets and favorable blocks of shale gas in the Guizhong Depression,the study concludes that the potential exploration targets of shale gas of the Luzhai Formation are distributed in the Nandan,Hechi,Luzhai,Lipu.In the northeastern part of Huanjiang,the Yingtang Formation shale gas potential exploration targets are located in Minglun Town and Luocheng.