流体注入临界应力下干热岩渗透率演化与诱导地震关联机制研究

干热岩储层改造时流体注入带来的诱导地震风险是干热岩资源开发中面临的严峻问题，对诱导地震机理的研究是前沿科学问题。目前对低渗储层改造区域与断层之间的渗流路径的演化特性研究不足，且现有研究对于储层与构造带伴生而接近临界应力状态的特点考虑不足。因此，本项目围绕流体注入临界应力下干热岩渗透率演化规律及其与诱导地震的关联机制这一科学问题开展研究：进行流体注入临界应力下干热岩的试验研究，得到渗透率和裂缝系统随时间的演化、不同流体压力下摩擦系数的变化；基于实验室数据与无量纲化方法，建立渗透率随流体压力扰动演化的断层激活模型、摩擦系数随流体压力变化的断层滑动模型；建立考虑渗透率演化与摩擦系数变化的蒙特卡洛模拟计算模型，结合尺度升级方法分析工程尺度流体注入致断层滑动、诱导地震的风险。本项目将推动对干热岩开采中诱导地震的基础机理认知，研究成果预期用于优化干热岩地热能开采方案，降低诱导地震风险。

Geothermal energy is a kind of clean energy, among which hot dry rocks make up a major part. Exploration of geothermal energy in hot dry rocks requires fluid injection to make reservoir economical, as for fluid injection has potential risk of inducing earthquakes, and it’s necessary to research on fluid injection induced earthquakes. This research focuses on permeability evolution of hot dry rocks under critical stress state during fluid injection and its relation with induced seismicity. Fluid injection into hot dry rock under critical stress state is performed at laboratory scale; permeability evolution with different fluid injection pressure is recorded, friction coefficients with different fluid injection pressure are recorded. Based on laboratory data, models of permeability and pore pressure disturbance are built, and models of fluid pressure diffusion and induced fracture reactivation are constructed. Based on experimental data and nondimensionalization methodology, models of fault reactivation due to reservoir permeability evolution and fault slip due to friction coefficient change are built. Monte Carlo simulation is employed to incorporate upscaled model to calculate fault slip probability. This research project will promote our understanding of the induced seismicity mechanism, and the outputs will help to optimize the exploitation scheme and to reduce the risk of induced earthquakes.