基于离散-连续介质模型的水-EGS传质传热机理及数值模拟研究

Hot dry rock (HDR) geothermal resource is clean, renewable, stable and with large abundance of storage, and enhanced geothermal system(EGS) represents the key technology for effective HDR heat utilization. Regarding the discipline of fluid flow and heat transfer in hot rock, as well as the “thermal-hydraulic-mechanical-chemical(THMC)” coupling mechanism as the central issues, firstly, under the condition of high temperature and pressure, the measurement of rock thermophysical properties and experiments of fluid flow-heat transfer are conducted to gain the relationship between stress and strain of hot rock, the evolution of seepage characteristics and the rule of mineral dissolution and precipitation. Based on the experiment results, the discipline of fluid flow and heat transfer in hot rock and the response mechanism are revealed. Then, a multi-zone coupling model is constructed, based on discrete-continuum theory, to describe near bore fracture network zone-original surrounding rock zone-transition zone. Coupling boundary conditions are derived through the equation of mass, momentum and energy. With the Combination of multi-zone coupling model and Coupling boundary conditions, a THMC coupling model based on local non-thermal equilibrium theory in a water-EGS system is established and validated. Finally, the fast decoupled algorithms of large-scale systems which is strongly nonlinear for numerical solving is optimized and the program is developed. The study will enrich and expand the kinetics, thermodynamics and reaction kinetics database of heat extraction from hot rock, and also form a numerical simulation method to simulate mass transfer and heat transfer in the hot dry rock, as well as a policy is provided for optimizing the methods of hot dry rock development and operation parameters of EGS.

干热岩地热资源是清洁、稳定、安全、资源量巨大的可再生能源，增强型地热系统(EGS)是实现干热岩地热能开发利用的关键技术。本项目以水-高温岩体流动换热规律及其温度场、渗流场、应力场和化学场耦合作用机制的基础科学问题为核心，首先开展高温高压条件下岩样热物性参数测试及流动换热实验，阐明高温岩体应力-应变关系、渗流特征演化及矿物溶蚀/沉淀规律，揭示水-岩流动换热规律及响应机制；其次，基于离散-连续介质理论提出表征干热岩近井压裂区-原状围岩区-过渡区多重子区域耦合模型，并遵循质量、动量和能量守恒定律推导耦合边界条件，建立考虑局部非热平衡的水-EGS传质传热THMC耦合数学模型；最后，研究大型强非线性系统快速解耦算法及程序开发。预期成果将丰富和发展干热岩注水循环取热过程动力学、热力学及反应动力学，形成干热岩EGS多物理场耦合数值模拟方法，为优选干热岩地热能开发方式、优化EGS运行参数提供理论基础。

干热岩地热资源是清洁、稳定、安全、资源量巨大的可再生能源，增强型地热系统(EGS)是实现干热岩地热能开发利用的关键技术。本项目以水-高温岩体流动换热规律及其温度场、渗流场、应力场和化学场耦合作用机制的基础科学问题为核心，首先，通过实验研究，阐明了高温岩体冷水注入条件下岩体应力-应变规律、渗流特征演化特征及溶蚀/沉淀规律及相互关联性，揭示了水-EGS 系统 THMC 多物理场相互影响机制，丰富和扩展热力学及反应动力学数据库。然后，基于离散-连续介质理论，构建并推导表征干热岩近井压裂缝网区-原状围岩区-过渡区多重子区域耦合模型及子域间耦合边界条件，建立了考虑局部非热平衡的水-EGS 传质传热 THMC 耦合数学模型。最后，通过理论推导建立水-EGS系统THMC多物理场耦合传质传热数学模型，优选大型强非线性系统的高效数值求解算法并开发水-EGS 多场耦合数值模拟程序。依托项目研究成果，与中石油勘探开发研究院海外中心合作，相关研究成果在中非乍得Bangor盆地地热田先导试验区开发方案编制和开发试验中得到了转化应用，有效支撑了项目顺利实施。在本项目资助下，项目组成员在国内外重要期刊和重要会议上发表学术论文21篇（其中，SCI、EI收录18篇，中文核心3篇），申请了国家发明专利3件，登记软件著作权1项。培养了包括“孙越崎优秀学生奖”在内的博士、硕士研究生8名，圆满完成了项目要求的预期成果。