四川盆地开江—梁平海槽内发现大隆组

DALONG FORMATION FOUND IN KAIJIANG-LIANGPING OCENIC TROUGH IN THE SICHUAN BASIN

四川盆地广元一旺苍海槽、城口一鄂西海槽和开江-梁平海槽具有相同的上二叠统一下三叠统飞仙关组的沉积相序组合，它们在长兴晚期-飞仙关早期都是深水沉积区。其中前者上二叠统顶部是由含放射虫、骨针、有孔虫和腕足等二叠纪生物化石的硅质岩、硅质灰岩和硅质泥岩等组成的大隆组。而在此之前深埋于地腹中的后者一直没有识别出大隆组。最近通过钻井地层测井对比分析和钻井岩屑薄片研究发现开江-梁平海槽区飞仙关组底部高自然伽马、低电阻层段是由含放射虫、腕足、有孔虫等晚二叠纪生物化石的硅质岩、硅质灰岩、硅质泥岩组成的，应划分为上二叠统大隆组。开江-梁平海槽区大隆组厚12．5～33．5m．平均有机碳含量达3．88形．是优质的烃源岩。与海槽相邻的台地边缘相带是大中型气藏的有利分布区。

The Guangyuan-Wangcang Trough, the Chengkou-E'xi Trough and the Kaijiang-Liangping Trough are regions with deep water sediments of the Upper Permian-Lower Triassic System in the Sichuan Basin. The depositional sequences form the Upper Permian-Lower Triassic are the same in these troughs. There is Dalong Fm consisting of silialite, siliceous shale and siliceous limestone with fossil debris of radiolarians, brachiopods, foraminifers and so on in the exposures outcrops of the Guangyuan-Wangcang Trough, the Chengkou-E'xi Trough. But the Dalong Fm. has not been discerning until quite recently in the Kaijiang-Liangping Trough. According to stratigraphic correlation and well cuttings sample sections research of the Kaijiang-Liangping Trough, the Feixianguan Fm. Lowest sections with high gamma ray curve and low electric resistance are silialite, siliceous shale and siliceous limestone with Upper Permian epoch fossil as radiolarians, brachiopods, foraminifers, etc. So that ought to be classified to be the Upper Permian Dalong Fm. The thickness of the Dalong Fm ranges from 12.5 to 35.5 m in the Kaijiang-Liangping Trough and it's the excellent source rocks having the average organic carbon content of 3.88% in the Sichuan Basin.