沉积环境对页岩气储层的控制作用——以中下扬子区下寒武统筇竹寺组为例

摘要

According to the assumption of "deposition control facies,facies control reservoir",based on field investigation,experimental test and previous research results,a study was performed to investigate the characteristics of shale reservoir controlled by the sedimentary environment of the Lower Cambrian Qiongzhusi Formation in the Middle Lower Yangtze area.The studies show that the organic-rich shale is mainly developed in the shelf facies and deep-sea retention basin facies,the thickness of deposition center is up to 100-180 m with the maximum organic carbon content of 18.7％,and the average organic carbon content is 5.07％.The major lithologies include organic-rich carboniferous shale,siliceous shale,silty shale and calcareous shale under anoxic environment.The minerals of the shale are mainly quartz(average 64.97％) and clays(average 23.66％).A large number of intergranular holes of pyrite under the anoxic environment,microporosity produced by hydrocarbon generation in organic matter,microporosity between layers of clay minerals and micro-cracks controlled by brittle mineral provide a good reservoir space for shale gas.Therefore,the studies on the development of reservoir characteristics under the control of the environment will provide a substantial basis for shale distribution,organic matter abundance,reservoir space and favorable area evaluation in shale gas exploration and development.%以“沉积控相,相控储层”为研究思路,基于野外露头实测、室内试验测试以及结合前人研究成果,探讨中下扬子区下寒武统筇竹寺组沉积环境对页岩气储层的控制作用.研究表明:中下扬子区下寒武统筇竹寺组富有机质泥页岩主要发育于陆棚相和深海—次深海滞留盆地相中,沉积中心页岩厚度可达100～180 m,有机碳含量(TOC)最高可达18.7％,平均达到5.07％；静水缺氧还原沉积环境岩石类型主要以富含有机质的炭质页岩、硅质页岩、粉砂质页岩以及钙质页岩为主,页岩矿物成分以石英(平均达64.97％)和黏土矿物(平均达23.66％)为主；缺氧还原环境下沉积的大量黄铁矿形成的黄铁矿晶间孔、有机质生烃形成的微孔隙、黏土矿物层间微孔隙以及脆性矿物控制的微裂缝为页岩气提供了良好的储集空间.沉积环境控制下储层发育特征的研究可为页岩展布、有机质丰度、储集空间以及后期有利区评价等研究提供基础.