中国南方海相富有机质页岩孔隙特征及其对页岩气储集与扩散迁移的制约

Shale gas has become one of the most important unconventional energy resources. Commercial development of shale gas has been gotten in marine organic-rich shale from South China. There are great potentials of shale gas resource in these organic-rich shales. But the understanding for the enriched rule of shale gas remains unclear. The pore system in organic-rich shales is the storage site for shale gas, and its formation and evolution is the key to insight into the enriched rule. This proposal aims to disclose the pore system and evolution, gas reservoir mechanism, and migration and enrichment of adsorbed mathane in continuous gas reservoirs of marine organic-rich shales in South China through the research of their material components, micropore structure, methane adsoption capacities and adsoption thermodynamics. The results from this research may provide theoretical supports for us to explore and evaluate shale gas resource in China.

页岩气已成为重要的非常规接替能源。中国南方海相富有机质页岩已实现页岩气的商业开发，具有巨大的资源潜力，但对其中页岩气富集规律和扩散迁移机制的研究严重滞后。富有机质页岩的孔隙体系是天然气储集的场所，其形成演化是揭示页岩气富集规律的关键之一，同时，孔隙结构的非均质性控制了页岩气的扩散迁移方式，进而制约了页岩气的富集和开发效率。本申请试图通过不同特征富有机质页岩的物质组成、显微孔隙类型、结构与演化、吸附CH4气的能力、表面吸附热力学及扩散迁移方式等方面的研究，揭示中国南方海相富有机质泥页岩孔隙体系的发育特征、主控因素和演化规律；阐明页岩储层孔隙体系对天然气赋存状态、储气性能的影响；探索连续性页岩气藏不同孔隙特征富有机质页岩储层中页岩气扩散迁移和富集的机理；为页岩气勘探开发和资源评价提供科学的理论依据。

本项目在多条野外露头剖面考察、钻井岩心观察取样的基础上，通过场发射扫描电镜（FE-SEM），聚焦离子束扫描电镜（FIB-SEM）对页岩显微孔隙特征进行了定性观察，通过高压压汞，低压氮气吸附，低压二氧化碳吸附，高压甲烷吸附、小角度和超小角度中子散射技术（SANS/USANS）等方法对页岩孔隙体积和孔隙结构进行定量表征。通过渗透率实验、润湿角实验、流体的自发吸入实验、示踪剂的饱和扩散实验，水蒸气吸附实验等方法探讨了气体在页岩中的扩散迁移情况。通过上述研究，查明了富有机质页岩沉积环境与有机质富集机制，揭示了富有机质页岩的孔隙特征和演化，特别是有机质孔隙的演化及储集贡献，探讨了富有机质页岩物质组成与显微孔隙结构的关系，显微孔隙结构与吸附能力的关系，富有机质页岩物质组成与吸附能力的关系，揭示了中国南方海相富有机质泥页岩天然气吸附机理及其主控因素，建立了页岩气储层吸附储气性能评价方法，初步查明了页岩气扩散迁移的制约机制，为页岩气勘探开发和资源评价提供科学的理论依据。