下扬子地区五峰组-高家边组页岩气形成条件

Geological Conditions of Shale Gas in the Wufeng-Gaojiabian Formations in Lower Yangtze Area

页岩气是一种清洁、高效的非常规能源。通过露头观测、钻井资料、有机地化与储集物性等资料，分析了下扬子地区上奥陶统五峰组一下志留统高家边组页岩的沉积环境、厚度、分布、埋深、有机质丰度、类型、热演化程度、孔缝特征及岩石矿物组成等。研究结果表明，该页岩主体为陆棚沉积，沉积厚度大，主要分布在300～400m之间、埋深适中；页岩有机碳含量主要分布在0．5％～1．0％之间，有机质类型为I型和II型。镜质组反射率主体分布在1．5％-2．5％之间，处于高成熟一过成熟阶段；页岩石英含量较高，普遍分布在34.2％～55．1％之间，微裂缝发育。有利于压裂改造。研究表明页岩气形成的有利区分布在苏北高邮一海安一句容、皖南泾县一宁国和浙西临安等地区。

Shale gas is a clean, efficient unconventional energy resource, therefore, it is of great significance to acc, elerate the shale gas exploration in Lower Yangtze Area to adjust the energy structure in China. Based on the outcrop, the well data, the geochemical and reservoir property in Lower Yangtze Area, this paper analyses the sedimentary environment, the thickness, distribution, the buried depth, the organic matter contents and types, the maturity and the reservoir characteristics of shale in Wufeng-Gaojiabian Formations of Upper Ordovician to Lower Silurian. It is shown that the Upper Ordovician Wufeng Formation-Lower Silurian Gaojiabian Formation of Lower Yangtze Area is formed in shelf sedimentm＇y environments with a thickness of 300-400m in a moderate depth. Wufeng-Gaojiabian Formations contain 0.5% to 1.0% of organic carbon, consistent with typeland II kerogen. The vitrinite reflection values R,, are in tile range of 1.5%-2.5%, indicating a high mature to over mature stage for gas generation. The quartz content in the mineral ranges from 34.2% to 55.1% in this set of shale with rich micro-fracture, which is good for fracturing. The thickness of shale, the buried depth, the organic carbon and the maturity show that Gaoyou-Haian-Jurong of Northern Jiangsu, Jingxian-Ningguo of Southern Anhui, Linan of Western Zhejiang areas are considered favorable zones for the shale gas formation.