EGS近井区域渗流特性对工质循环路径的影响机制研究

增强型地热系统（EGS）以开采地下3-10km干热岩中热能、用于地面发电为目标，代表着一种极富潜力的清洁可再生能源利用技术。近井区域渗流特性将影响EGS工质压力场分布及循环路径，进而决定EGS产能和寿命。本项目将结合细观裂隙尺度和宏观热储尺度模型，研究近井区域渗流特性与井筒、远井区渗流的耦合效应，探讨近井区域等效渗透率分布对工质循环路径的影响机制。优化近井区域等效渗透率分布特征，实现降低井间流阻并抑制流体短路。同时本项目将在实验室开展EGS仿真实验，实验结果用于验证和进一步完善多尺度模型。实验验证后的多尺度模型研究结果将被应用于模拟研究实际EGS（Soultz EGS）近井区域渗流影响下的采热过程，为更优近井区域压裂工艺、地下热储改造提供指导性建议。项目研究成果可以提升人们对近井区域渗流特性的基础认知，为相关关键技术发展提供理论指导，多尺度模型预期将成为EGS研发和设计、优化的有效工具。

Enhanced or engineered geothermal system (EGS), aiming to mine heat from low-permeability crystalline hot dry rocks located at 3-10 km depths below surface for earth-surface power generation, represents a very promising clean and renewable energy utilization technology. The seepage flow properties in the near wellbore region impact pressure distribution and circuit path of working fluid, and further determine the capacity and lifetime of EGS. This project will develop mesoscopic fracture-level model and macroscopic heat reservoir-level model, which can be used to study the coupling effect among the seepage characteristics in the near wellbore region, far well area and flow in the wellbore. We will further investigate the mechanism of the influence of equivalent permeability distribution of the near wellbore region on the working fluid circulation path. Then the permeability distribution can thus be optimized to reduce flow resistance between wells and suppress fluid short circuit. Meanwhile, we will carry out laboratory-scale EGS experiments to validate and perfect the multi-scale models, which will be used to study heat extraction processes in a real EGS (e.g. Soultz EGS). The goal is to obtain more optimized heat extraction strategies and provide suggestions for the improvement or reconstruction of near-well region of heat reservoir. Results from this project will improve fundamental understanding of near-well seepage flow properties and provide a theoretical basis for the development of relevant key technologies. The multi-scale models are expected to act as an effective and powerful tool for the research and development, design and optimization of EGS.