陆相页岩储层岩石组构和孔隙结构特征及其对含气性的控制机理

The continental organic-rich shale is widely distributed with huge exploration potential of shale gas in China. But compared with the exploration and development of marine shale gas, the continental shale gas lags behind the weak theoretical research on the shale gas enrichment . The efficient development of continental shale gas is of great significance to mitigate the contradiction between the supply and demand of natural gas in China. In this project, the continental shale from Jurassic Formation in northeastern Sichuan Basin are studied, and the control mechanism of structural fabric and pore structure on shale gas accumulation are studied. Detailed geochemical and mineralogical approaches are utilized to determine the characteristics of structural fabric and divide lithofacies types. Both indirect measurement and direct observation methods are conducted to characterize the pore structures hosted by organic matter and minerals, and the correlation between pore structure and organic geochemistry, mineral composition and sedimentary structure are discussed. Using molecular dynamics simulation and methane adsorption experiments, the control mechanism of structural fabric and pore structure on shale gas occurrence is determined, and the critical pore radius for free gas occurrence in different types of pore hosted by organic matter and minerals are simulated, the dominant controlling factors of shale gas content in different lithofacies are clarified, and shale gas content prediction model and gas enrichment mode are established. The expected results of this project are of great significance for the continental shale gas exploration and development.

我国陆相富有机质页岩分布广泛，具有巨大的页岩气勘探潜力，但与海相页岩气相比，陆相页岩气勘探开发进展滞后，其根本原因在于陆相页岩气富集理论研究薄弱，高效开发陆相页岩气对缓解我国天然气供需矛盾具重要意义。项目以川东北地区侏罗系陆相页岩为研究对象，针对页岩岩石组构和孔隙结构对页岩含气性的控制机理这一科学问题开展研究。通过地球化学测试、全岩矿物分析，阐明页岩岩石组构特征，划分岩相类型；采用间接测试和直接观察相结合的方法，表征页岩多尺度孔隙结构特征；通过研究页岩孔隙结构与有机地化、矿物组成和沉积构造特征的关系，阐明页岩孔隙结构控制因素；通过分子动力学模拟和甲烷吸附实验，确定页岩不同基质孔隙游离气赋存的临界孔径，揭示页岩岩石组构和孔隙结构对含气性的控制机理，阐明陆相页岩含气性的主控因素，建立页岩含气量预测模型及控气模式。研究成果对丰富页岩气富集地质理论，指导陆相页岩气勘探开发具有重要的理论和现实意义。

本研究在采集陆相页岩样品和收集资料的基础上，明确了页岩沉积构造特征，确定了页岩有机地化特征和矿物组成特征；在明确页岩有机地化特征、矿物组成特征与沉积构造特征三者的基础上，对陆相页岩岩相进行了划分，明确了不同岩相页岩岩石组构特征差异。利用FE-SEM、FIB-SEM等直接表征页岩孔隙结构特征，同时利用气体吸附法结合压汞法间接定量表征了页岩孔隙结构，完善了陆相页岩储层孔隙结构表征体系和表征方法，综合确定了陆相页岩多尺度孔隙结构特征。采用单因素控制分析法，分别查明了有机地化特征、矿物组成特征和沉积构造特征对孔隙结构发育的控制作用。在查明陆相页岩储层孔隙结构发育特征及其控制因素的基础上，识别了不同岩相页岩储层孔隙类型、大小、孔径分布、连通性、比表面积和孔体积等孔隙结构参数，明确了不同页岩孔隙结构特征差异性并查明导致其差异的控制因素。通过分子动力学模拟和不同有机质、不同矿物的样品高压甲烷等温吸附实验，阐明了陆相页岩储层岩石组构及其介质界面效应对页岩气吸附的控制机制以及微观孔隙结构对页岩气赋存状态和含气量的控制机制，综合考虑岩石组构和孔隙结构的影响，确定了不同岩相页岩储层游离态页岩气赋存的临界孔径，揭示了陆相页岩岩石组构和孔隙结构对含气性的控制机制，明确了不同岩相页岩中游离气与吸附气的非均质性分布特征，阐明了不同岩相页岩含气性主控因素，并明确了不同岩相页岩含气性主控因素差异；建立了陆相页岩储层总含气量预测模型，预测了典型井目的层段页岩储层总含气量。在本基金赞助下研究期间共发表论文26篇，出版专利1部，授权专利8件，获得国家级一等奖2项，省部级一等奖2项。