CO2页岩气藏封存与强化页岩气开采的固流耦合机制研究

Based on multi-disciplinary compromise and overlapping among physics, mechanics and chemistry, theoretic and experimental studies on failure criterion and deformation characteristics of rock matrix and fracture, caused by CH4,multiphase CO2（supercritical phase and gas phase）, and CO2/ CH4 mixtures flow and the change of stress and temperature fields, will be conducted. Constitutive relationships, considering inherent heterogeneous deformation, for porous and fractured rock, will be set up. The flow model describing the coupling motion law of multiphase flow through deformable porous and fractured medium will be developed. Strain induced by multiphase multicomponent fluid for porous and fractured rock will be explained. Physical mechanism causing the evolution of permeability and porosity in gas shales will be proposed, and corresponding relationship model will be obtained. The project aims at getting further insight into the coupling mechanisms between shale rock deformation and multiphase multicomponent fluid transport in porous and fractured rock, and providing a theoretical support for the performance of CO2 sequestration with enhanced gas recovery in shale gas reservoirs.

基于物理-力学-化学多学科交叉理论分析，结合实验研究，探索不同应力和温度条件下CH4、多相态CO2（超临界态和气态）及其混合物作用下页岩基质与孔隙裂隙的变形特征与破坏准则，提出可以考虑内部差异性变形的孔隙裂隙介质物理力学本构关系，研究多相多组分流体在页岩储层中的耦合流动规律，揭示多相态多组分流体引起的孔隙裂隙介质的应变机理，得出孔隙裂隙介质孔隙度、渗透率等参数演化的真实物理力学机制，建立相应的关系模型。 预期通过本项目的研究，进一步深入认识复杂应力条件下孔隙裂隙介质物理力学行为及其与多相多组分流体运移的耦合机理，为CO2页岩气藏封存与强化页岩气开采提供理论支撑。

页岩气作为非常规能源，其赋存条件复杂、开采技术要求高，目前国内仅少数地区实现了页岩气商业开采。为提高页岩气开采率，缓解温室气体CO2的减排压力，开展CO2页岩气藏封存与强化页岩气开采研究具有重要的理论和实际意义。首先，本项目自主研发了一套岩石多功能渗流测试系统，基于该试验系统开展了不同应力和温度作用下，CH4、CO2及其混合物吸附/解吸、渗流、驱替等试验，得到了不同孔压、有效应力、温度等条件下的页岩渗透演化规律，建立了考虑吸附基质膨胀、有效应力、滑脱作用的渗流理论模型；分析了多相多组分流体下的页岩等温吸附和竞争吸附特征，研究了CO2置换CH4过程及机理，提出了优化的瞬态脉冲方法，建立了基于瞬态脉冲法的非线性渗流分析方法；研究了多场耦合作用下页岩孔隙裂隙生长、演化、贯通机制，提出了孔隙裂隙介质物理力学行为与渗透率的关系模型；显微观测了超临界CO2作用后页岩微观结构变化特征，建立了固-流-热耦合条件下CO2驱替CH4的渗流、扩散、吸附/解吸模型，模拟了页岩储层注入CO2驱替CH4过程，揭示了CO2驱替页岩气的传质机制。研究结果为CO2页岩气藏封存与强化页岩气开采提供了理论支撑。