扬子地块上二叠统龙潭组页岩气勘探前景

扬子地块是中国南方进行油气勘探研究较早的地区之一，在古生代，扬子地块发育了以下寒武统、上奥陶统-下志留统、上二叠统和下二叠统为代表的8套黑色泥页岩。近几年，人们对下寒武统筇竹寺组和上奥陶统-下志留统五峰组-龙马溪组海相泥页岩做了较多的基础性研究工作，而对上二叠统龙潭组海陆交互相泥页岩则尚缺乏评价。为此，根据前人的研究成果和野外地质调查资料，分析了扬子地块上二叠统龙潭组泥页岩的发育特征，探讨了龙潭组页岩气的勘探开发前景。结论认为：①龙潭组黑色页岩具有有机碳含量较高、热演化成熟度达高成熟度阶段、石英含量达40%左右、厚度介于20～200 m、吸附能力强等有利条件，与美国圣胡安盆地Lewis页岩很相似，具有较好的页岩气勘探开发潜力，但黏土含量高、非均质性强、后期改造作用强烈等又会对其页岩气富集产生不利的影响；②龙潭组页岩气成藏条件纵向上：中、上段优于下段，横向上页岩气勘探的有利地区为上扬子川中、川东、渝西北和下扬子苏南地区。

Prospect of shale gas exploration in the Upper Permian Longtan Formation in the Yangtze Massif

The Yangtze massif is one of the areas in South China where oil and gas exploration started very early. Eight sets of black mud shales, including the Lower Cambrian, Upper Ordovician Lower Silurian, Upper and Lower Permian, etc. were deposited on the Yangtze massif during the Paleozoic era. In recent years, a lot of basic studies have been carried out on the marine mud shales in the Lower Cambrian Qiongzhusi Fm and the Upper Ordovician Lower Silurian Wufeng Longmaxi Fms. In contrast, few studies have been conducted on the transitional shale in the Upper Permian Longtan Fm. In view of this, based on the previous research results and field geologic survey data, this paper analyzes the development characteristics of the Upper Permian Longtan Fm shale, and also discusses its prospect. The black shales in the Longtan Fm are featured by relatively high TOC, high thermal maturity, about 40% of the quartz content, thickness of 20 ~ 200 m, and strong adsorption capability, all being favorable conditions for shale gas accumulation and indicating a high shale gas potential there quite similar to the Lewis shale in the San Juan Basin (USA). However, its high clay content, strong heterogeneity, and strong later stage tectonic modification have an adverse effect on shale gas enrichment. Vertically, the upper and middle members are more favorable for shale gas exploration than the lower member in the Longtan Fm, while horizontally the central and eastern Sichuan Basin and northwestern Chongqing in the Upper Yangtze as well as the southern Jiangsu in the Lower Yangtze are favorable for shale gas exploration.