川东忠县—鱼池地区二叠系—三叠系海槽相、台缘相的发现及勘探意义

川东—鄂西地区晚二叠世—早三叠世发育开江—梁平海槽与城口—鄂西海槽,明确环海槽分布的台地边缘及沉积相带展布对指导二叠系—三叠系礁滩气藏的勘探开发具有重要现实意义。基于川东忠县—鱼池地区窑厂、千野草场、楠木桠和三墱坡剖面长兴组—飞仙关组的现场实测和系统取样分析,结合钻井资料和建南地区前期研究成果,认为大池干—石宝寨—高峰场区块为开阔台地相沉积,而开江—梁平海槽主体未向该区延伸;忠县—鱼池地区发育海槽相深水沉积,开江—梁平海槽与建南地区浅水陆棚直接相连,向东直接连通城口—鄂西海槽主体,其两侧发育台地边缘相礁滩沉积。通过确定台地边缘平面展布规律,进一步扩展了研究区内台地边缘分布范围,为川东地区二叠系—三叠系礁滩气藏的勘探开发揭示了全新的领域。

Discovery and exploration significance of Permian-Triassic trough and platform margin facies in Zhongxian-Yuchi area,eastern Sichuan Basin

The Kaijiang-Liangping trough and the Chengkou-western Hubei trough were developed in the Late Permian-Early Triassic eastern Sichuan Basin-western Hubei area. To determine the distribution of platform margin and sedimentary facies surrounding the trough has an important realistic significance for guiding the exploration and development in Permian-Triassic reef and shoal gas reservoirs. Based on the field measurement and systematic sampling analysis of Changxing-Feixianguan Formation on Yaochang, Qianyecaochang, Nanmuya and Sandengpo outcrops in Zhongxian-Yuchi area, eastern Sichuan Basin, in combination with the well drilling data and early research achievement of Jiannan area, Dachigan-Shibaozhai-Gaofengchang block is considered as the opening platform facies sediment, while the main body of Kaijiang-Liangping trough has not extended to this area. The trough facies deep-water sediment is developed in Zhongxian-Yuchi area, and the Kaijiang-Liangping trough is directly connected with the shallow shelf in Jiannan area, directly contacting the main body of Chengkou-western Hubei trough eastwards with platform edge facies reef and shoal sediment on both sides. Through determining the plane distribution rule of platform margin, the platform margin distribution range in the study area has been further extended, which reveals a brand new field for the exploration and development in the Permian-Triassic reef and shoal gas reservoirs of eastern Sichuan Basin.