干热岩开发中高温水-岩作用下岩石应力腐蚀及多场损伤问题

赋存于地球深部的地热资源,以其储量丰富、清洁再生等优势,有望成为破解我国能源困局,助推“双碳”目标实现的重要途径之一。干热岩(HDR)开发过程中,面临着高温高压环境下水-岩作用问题,在温度场、渗流场、应力场、化学场(THMC)等多场耦合作用下,岩体应力腐蚀效应和疲劳劣化会诱发岩石微裂纹-裂缝扩展、成核与丛集行为,进而影响增强型地热系统(EGS)的热交换效率和地质体稳定性,这也是制约干热岩长期安全开发的瓶颈,亟待突破。通过总结现有干热岩高温高压下多场损伤研究中的实验探索、理论模型、数值分析等多手段跨尺度方法,分析干热岩在高温高压及水环境下的应力腐蚀效应,可阐明循环生产过程中低温工质与高温地质体循环换热下干热岩储层结构演化的动态过程及工程响应,进而揭示THMC多场耦合作用下干热岩储层疲劳劣化损伤机理,为我国深部地热资源高效安全开发提供理论支撑和地质保障; 但仍亟待深入开展增强型地热系统的THMC多场耦合作用下岩体应力腐蚀效应的干热岩疲劳劣化机制与长期稳定性研究,如考虑应力腐蚀效应和疲劳损伤的干热岩长期强度评价模型、基于跨尺度疲劳损伤评价的干热岩开发下地质体长期稳定性方法、适应于干热岩储层改造及裂缝网络演化下THMC多场耦合数值方法。

Fatigue Deterioration and Multi-field Damage to Rocks Under High Temperature Water-rock Interaction in Hot Dry Rock Development

Geothermal resources, which are located deep in the Earth, are expected to become one of the important ways to break China's energy dilemma, and promote the realization of carbon peak by 2030 and carbon neutrality by 2060 with the advantages of abundant reserves, clean and renewable. In the process of developing hot dry rock(HDR), the problem of water-rock interaction under high-temperature and high-pressure environment is faced. Under the coupling action of multiple fields such as thermal-hydraulic-mechanical-chemical(THMC), the stress corrosion effect and fatigue deterioration of rock mass will induce rock micro-cracking and fracture expansion, nucleation and clustering behavior, which will affect the heat exchange efficiency of enhanced geothermal system(EGS)and stability of geological body. This is the bottleneck that restricts the long-term safe development of HDR and needs to be broken. Based on experimental exploration, theoretical modeling, numerical analysis and other multi-measures, cross-scale methods for multi-field damage study on HDR under high-temperature and high-pressure, the stress corrosion effect of HDR under high-temperature, high-pressure and water environment was analyzed, the dynamic process and engineering response of the structural evolution of HDR reservoir were elucidated in the cyclic production process of low-temperature mass and high-temperature geological body cyclic heat exchange, and then the fatigue deterioration damage mechanism of HDR reservoir under THMC multi-field coupling was revealed, and the theoretical support and geological guarantee for the efficient and safe development of deep geothermal resources in China were provided. However, it is still urgent to carry out further research on the fatigue deterioration mechanism and long-term stability of HDR under the stress corrosion effect of rock mass and THMC multi-field coupling action of EGS, such as the long-term strength evaluation model considering stress corrosion effect and fatigue damage, the evaluation method of long-term stability based on cross-scale fatigue damage, and THMC multi-field coupling numerical method for reservoir reconstruction and fracture network evolution.