湖北长阳地区有机质热演化异常成因及意义

CAUSES AND SIGNIFICANCE OF ABNORMAL THERMAL EVOLUTION OF ORGANIC MATTERS IN CHANGYANG AREA,HUBEI PROVINCE

对湖北长阳地区上震旦统—下三叠统系统的镜质体(沥青)反射率和伊利石结晶度测试分析表明,在二叠系—志留系上部和志留系底部—下寒武统上部存在2个等效镜质体反射率和伊利石结晶度异常带。综合分析认为,上部异常带为平流热液流体沿云台观组(D2y)、纱帽组(S3sh)等砂岩储层和D2y/S3sh、岩关组(C1y)/泥盆系等不整合面流动的热效应所致;下部异常带为热液流体在石龙洞组(-C1s)—奥陶系储层中形成热对流造就。燕山期热液流体的热效应使区内二叠系、五峰组—龙马溪组烃源岩理论上在中三叠世末停滞的生烃作用持续至侏罗纪末,延长了烃源岩生烃时期,有利于油气聚集。

Studies of vitrinite reflectance and illite crystallinity from Upper Sinian to Lower Triassic in Chang-yang area of Hubei Province have indicated that,there are 2 abnormal zones of equivalent vitrinite reflectance and illite crystallinity between Permian-top of Silurian and bottom of Silurian-top of Lower Cambrian.The upper abnormal zone is formed by thermal effects of advection hot liquid flowing along D2y,S3sh sandstone reservoir as well as D2y/S3sh,C1y/D unconformity surface.The lower abnormal zone is formed by thermal convection of hot liquid in-C1s-O reservoir.Hydrocarbon generation in P and O3w-S1ln should stop at the end of Middle Triassic;however,due to thermal effect of hot liquid during the Yanshanian stage,it continues to the end of Jurassic,hence favorable for petroleum accumulation.