渝东南地区下志留统龙马溪组页岩气成藏地质特征

摘要

In recent years,the exploration and development of shale gas in Southeast Chongqing has become the focus of oil and gas exploration in China.In this article,the geologic characteristics of shale gas accumulation in Longmaxi Formation in the southeast of Chongqing were systematically analyzed in terms of stratigraphic sedimentation,geochemistry,reservoir characteristics and reservoir pattern.The results show that the shale thickness of the Longmaxi Formation in the southeast of Chongqing is larger,ranging from 30 to 130 m.The sedimentary center,where the organic carbon content of shale is high (about 0.05％-17.4％),is in the Shizhu-Pengshui area,so it is the area with high organic carbon in Pengshui.The type of organic matter is dominated by amorphous sapropelic matter,and the degree of thermal evolution reaches high-over maturity.The mineral composition of the reservoir is complex.The clay minerals are composed of illite,mixed-layer minerals of illite and montmorillonite and chlorite.The brittle minerals include quartz,feldspar and carbonate minerals and the brittleness index is high.The storage space is dominated by organic pores,intergranular pores,intragranular pores,pores between interlayered clay minerals and fractures.Shale gas accumulated in situ to form a gas reservoir,and the gas was mainly generated from crude oil cracking and organic matter pyrolysis.%近年来,渝东南地区页岩气勘探开发成为油气勘探领域的焦点.基于野外实测地层剖面和钻井资料,从页岩地层特征、地球化学特征、储层特征及成藏模式等方面系统分析了渝东南地区龙马溪组页岩气成藏地质特征.结果表明:渝东南地区龙马溪组页岩沉积厚度大,为30 ～ 130 m,在石柱—彭水地区形成沉积中心;页岩有机碳含量高,为0.05％～ 17.4％,在彭水地区形成有机碳含量高值区,有机质类型主要以腐泥质无定性体为主,热演化程度处于高—过成熟阶段.储层矿物成分复杂,粘土矿物包括伊利石、伊/蒙混层和绿泥石,脆性矿物以石英、长石和碳酸盐矿物为主,脆性指数高.储集空间以有机质孔、粒间孔、粒内孔、粘土矿物层间孔及裂缝为主.页岩气成藏方式为原地聚集成藏,生气方式主要为原油裂解生气和有机质热解生气.