重庆及其周缘地区下古生界页岩气成藏条件及有利区预测

摘要

从野外地表露头、井下岩心及典型剖面等基础资料出发,以富有机质页岩形成地质背景及其展布特征-页岩气成藏条件-有利区预测为主线,对重庆及周缘地区下古生界页岩气成藏条件进行分析,并采用综合信息叠合法对该区有利区进行预测。指出研究区下寒武统筇竹寺组和上奥陶统五峰组—下志留统龙马溪组两套富有机质页岩普遍发育,分布广,厚度大,埋藏适中,有机质类型好,有机质含量高,具有充足的储集空间和运移通道,并且等温吸附模拟和现场解析实验也表明,这两套页岩均具有较强的气体吸附、较好的含气性能;多口井钻遇黑色页岩段气显异常普遍,也为页岩气的存在提供证据。总之,该区与美国东部典型页岩气盆地有诸多地质可比性,具有形成页岩气藏的有利地质条件,是页岩气勘探研究值得关注的重要领域。%The paper primarily studied geological background of organic-rich shale and its distribution characteristics,reservoir-forming conditions of shale gas and potential favorable areas of shale gas reservoir development.The study started from basic data such as the field surface outcrops,underground core and typical profile,and by the analysis of the reservoir-forming conditions of shale gas in the lower Paleozoic of Chongqing and its adjacent,and using comprehensive information method,the favorable areas for shale gas reservoirs were predicted.The results indicate that the Qiongzhusi Formation of Lower Cambrian system organic-rich shale,Wufeng Formation of Upper Ordovician system and Longmaxi Formation of Lower Silurian system organic-rich shale in the study area were characterized by wide distribution,great thickness,buried moderately,good organic type,high organic content,high organic thermal evolution degree and high hydrocarbon potentials.The shale is rich in brittle minerals,with great quantity of matrix micro-pore and cracks,and good reservoir conditions,which offered sufficient accumulated space and migration pathway for shale gas.The result of isothermal adsorption simulate test and well site desorption test showed that the two sets of black shale all have strong ability and high performance of gas adsorption.The widespread multi-stage gas shows of many wells drilled in the black shale strata in this area indicated the great potential of shale gas.In a word,the tectonic evolution characteristics and geological conditions in this area are similar to the typical shale gas basins in Eastern America,and the study area is a favorable and prospective place for shale gas exploration,having lots of advantages for forming shale gas reservoir.