鄂西-渝东地区克拉通内裂陷分布特征及油气勘探意义

Distribution characteristics of intracratonic rift and its exploration significance in western Hubei and eastern Chongqing area

利用野外露头、钻井资料结合震旦系-寒武系展布与岩相组合特征,提出鄂西-渝东地区发育"城口-巴东-五峰"克拉通内裂陷:①裂陷呈"沙漏"状近南北向展布,东西宽为60~280 km,南北长约为400 km;②裂陷形成于震旦纪陡山沱期,灯影期裂陷继承性发育,早寒武世早期为裂陷发育的鼎盛期,衰退于早寒武世中晚期,消亡于中寒武世;③受裂陷演化控制,裂陷内发育陡山陀组、筇竹寺组厚层优质烃源岩,其两侧发育灯影组、龙王庙组优质丘滩相及颗粒滩相白云岩储层,其中灯影组储层厚55~100 m,龙王庙组储层厚22~57 m。指出巫溪-奉节地区位于灯影组、龙王庙组丘滩相储集体叠合发育区,毗邻生烃中心,易形成旁生侧储、下生上储的有效成藏组合,应作为川东地区下步勘探的靶区。

Based on the field outcrop and drilling data,combined with the stratigraphic distribution and lithofacies associations of Sinian-Cambrian,it is proposed that“Chengkou-Badong-Wufeng”intracratonic rift develops in western Hubei-eastern Chongqing.The rift shows an“hourglass”shape,spreading from south to north with a width of 60-280 km from east to west and a length of about 400 km from north to south.The rift was formed in Doushantuo Period of Sinian,and developed in succession in Dengying Period.In the early stage of Early Cam⁃brian,it was the peak period of rifting development,and it declined in the middle and late stage of Early Cambri⁃an,and died out in the Middle Cambrian.Under the control of the evolution of the rift,there are thick and high quality source rocks in the Doushantuo Formation and Qiongzhusi Formation.The Dengying Formation and Longwangmiao Formation have high quality mound-shoal facies and grain shoal facies dolomite reservoirs on both sides of the rift,among which the Dengying Formation has a reservoir thickness of 55-100 m and the Long⁃wangmiao Formation has a reservoir thickness of 22-57 m.It is pointed out that Wuxi-Fengjie area is located in the superimposed development area of mounds and shoals reservoir of Dengying and Longwangmiao formations,adjacent to hydrocarbon generation center,which is easy to form two effective accumulation combination,one is the side product and side reservoir migrates toward the sides,the other is lower product and upper reservoir mi⁃grates vertically.And it should be the target area for further exploration in East Sichuan.