页岩非均质性和微-纳米孔喉结构对含气性的控制机理

Shale gas occurrence and gas content, which are closely related to shale heterogeneity and micro-nano scale pore-throat structure, are consider to be vital factors for shale gas resources evaluation and favorable target area optimization. However, the mechanism of interaction between them remains unclear. In this project, black shale from Silurian Longmaxi Formation in Yudongnan area are studied to discuss the control mechanism of shale heterogeneity and micro-nano scale pore-throat structure on shale gas bearing capacity. Detailed lithology and geochemistry approaches are proposed to determine the characteristics of shale heterogeneity. Indirect measurement and direct observation methods are conducted to characterize the micro-nano scale pore-throat structures hosted by organic matter and minerals, and the correlation of organic matter and mineral distribution with shale heterogeneous as well as the control of shale heterogeneity on micro-nano scale pore-throat structures are discussed. Using molecular dynamics simulation method, the critical pore radii for free gas occurrence in different types of pore throat hosted by organic matter and mineral are simulated. The control mechanism of micro-nano scale pore-throat structures on shale gas occurrence is determined and the shale gas in place is predicted. The expected results of this project are of great significance for control mechanisms of shale heterogeneity on micro-nano scale pore-throat structures on shale gas bearing capacity, shale gas in place evaluation, gas rich shale section prediction and favorable target area optimization.

页岩气的赋存状态和含气量是资源潜力评价、有利目标优选的关键因素。页岩的非均质性和微-纳米孔喉结构对页岩气的赋存状态和含气量有重要影响，但它们之间的相互关系及作用机理尚不清楚。项目以渝东南地区志留系龙马溪组页岩为研究对象，针对页岩非均质性和微-纳米孔喉结构对含气性的控制机理这一科学问题开展研究。通过岩石学和地球化学研究，阐明页岩非均质性特征；采用间接测试和直接观察相结合的方法，定量表征页岩的微-纳米孔喉结构；通过研究页岩微-纳米孔喉结构与页岩有机质和矿物非均质性分布的关系，阐明页岩非均质性对微-纳米孔喉结构的控制作用；通过分子动力学模拟，确定页岩有机质和矿物中不同类型孔喉赋存游离态甲烷的临界孔径，揭示页岩微-纳米孔喉结构对页岩气赋存状态的控制机理，预测页岩含气量。成果对于阐明页岩非均质性和微-纳米孔喉结构对含气性的控制作用，揭示页岩富气机理和评价页岩含气量具有重要理论和现实意义。

通过岩心描述、薄片鉴定和扫描电镜观测划分了页岩岩相，根据岩相分布的差异性，查明页岩的非均质性特征，采用有机和无机地球化学分析，明确页岩的沉积环境和成岩作用，阐明页岩非均质性的控制因素；利用压汞法和气体吸附法，间接定量表征页岩全孔径、全尺度微-纳米孔喉结构分布，利用FE-SEM、FIB-SEM、AFM、微区矿物定量分析仪等微-纳米尺度表征手段，直接观测了页岩微-纳米孔喉结构，定量分析了有机质和矿物中微-纳米孔喉结构的分布特征，完善了页岩储层微-纳米孔喉定量表征体系和表征方法；基于页岩不同基质中（有机质和无机质）微-纳米孔喉结构定量分布特征，研究了不同岩相页岩中有机质、矿物含量和分布的非均质性及孔喉结构类型和分布的非均质性，阐明了页岩非均质性对微-纳米孔喉结构的控制作用；基于兰纳-琼斯势能函数，通过分子动力学模拟，厘定了有机质和矿物中不同孔喉类型赋存游离态甲烷的临界孔径，揭示了非均质页岩中游离气与吸附气分布特征，阐明了页岩微-纳米孔喉结构对页岩气赋存状态的控制作用机理，确定非均质页岩的吸附气量与游离气量，通过建立页岩气含量预测模型，预测了页岩总含气量。在本基金赞助下研究期间共发表论文40篇（其中SCI 22篇），出版专利1部，申请专利24件（其中授权专利11件），获得省部级二等奖2项。