页岩储集空间演化特征及纳米孔隙中解吸与扩散的微观机制研究

Shale gas is a major strategic energy for China. Its efficient development is of great practical significance to relieve the contradiction of energy supply and demand, as well as guarantee the energy safety of country. For shale gas development in China, it is urgent to break through the shackle of low enhanced gas recovery (EGR). Therefore, on the one hand, we need to combine with the engineering practice to accurately describe the characteristics of reservoir space and its evolution rule. On the other hand, we need to reveal the occurrence state of shale gas in the reservoirs and desorption/diffusion of shale gas in the nanopore from the basic principles of mechanics. This project is carried out focusing on the experimental investigations, as well as organically combining numerical simulations and theoretic modeling in the mechano-thermal-chemical multifield coupled environment. First, the characteristics of shale reservoir space and its evolution rules would be studied, which is intended to uncover the full-field deformation of microscopic reservoir space in three dimensional, as well as the evolution mechanisms of pore structure. Then, studies on the occurrence state and the phase balance of shale gas in the reservoir space would be carried out, which is aimed to reveal the thermodynamic mechanism of phase balance between the adsorption gas and free gas. Third, the micro-mechanisms of desorption and diffusion in nanopore would be investigated, which is designed to clarify the multi-physical processes during the shale gas desorption and diffusion. This project targets to provide experimental basis and theoretical foundation for guiding the efficient exploitation of shale gas.

页岩气是我国重大战略性能源，其高效开发对于缓解我国能源供需矛盾、保障能源安全有极为重要的现实意义。我国未来页岩气的开发，亟待突破采收率低的桎梏。这在一方面需要结合工程实际，精确描述页岩储集空间特征及其演化规律；另一方面需要从力学基本原理出发，揭示储层中页岩气的赋存状态和纳米孔隙中页岩气解吸与扩散的微观机理。本项目拟以实验研究为主线，并有机结合数值模拟和理论建模的方法，在力-热-化学等多场耦合环境中：开展页岩储集空间特征及其演化规律研究，揭示微观储集空间的三维全场变形规律及孔隙结构的演化机制；进而探索微观储集空间中页岩气的赋存状态与相平衡规律，揭示吸附气和游离气复相平衡的热力学机理；开展纳米孔隙中解吸和扩散运移微观机制研究，廓清页岩气解吸与扩散运移的多物理过程。预期通过本项目的开展，为页岩气工业的高效开发提供实验基础和理论依据。

页岩气是我国重大战略性能源，其高效开发对于增强我国能源自主保障能力、推进能源技术革命、促进节能减排等具有十分重要的战略意义，是油气产量的新增长点。然而，由于我国页岩储层埋藏极深、构造复杂、低孔低渗、吸附量大，造成页岩气的采收率极低。我国未来页岩气的开发，亟待突破采收率低的桎梏。这在一方面需要结合工程实际，精确描述页岩储集空间特征及其演化规律；另一方面需要从力学基本原理出发，揭示储层中页岩气的赋存状态和纳米孔隙中页岩气吸附与解吸的微观机理。. 在本项目的资助下，项目组针对页岩微观储集空间特征及其动态演化、孔隙类型及孔径分布对气体赋存状态与相平衡的影响、孔隙结构和和分形特征对吸附与解吸的影响等三个关键科学问题，联合采用多种先进实验技术手段并有机结合数值模拟及理论建模方法，系统地厘清了页岩储层纳米孔隙的多尺度特征，揭示了页岩多尺度孔隙中气体随压力变化的赋存状态和相平衡规律；厘清了动态渗吸过程中各阶段的主导效应。基于搭建的超临界吸附实验平台，结合原位表征实验研究并阐明了超临界二氧化碳与页岩相互作用过程中物理吸附、缔合吸附和解离吸附导致纳米孔隙阻塞的微观机理。构建了目前国际上两种最大分子量的深成作用阶段的干酪根结构，建立了考虑吸附质分子间相互作用的超高压吸附模型。以上成果为为页岩油气的高效勘探和开发提供了重要参考。. 受本项目资助，在J. Petrol. Sci. Eng.、Energ. Fuel.、Glob. Chall.（封面）等相关领域国际权威期刊发表SCI论文9篇。多位国内外权威学者对项目组的研究成果进行大段、重点引用，包括数次完整引用多幅图片，并以我们的实验结果为标准开展进一步研究，重点强调了我们的相关结论，在国内外产生了较重要的学术影响。项目执行期间，项目负责人于2019年破格晋升为副研究员，并入选2020年度中国科学院青年创新促进会会员。