增强型地热系统（EGS）是指采用人工方法在地下3~10 km内的干热岩体中形成储层、通过灌输采热流体以开采出干热岩中热能用于地面发电的地热利用系统，是一种极富潜力的可再生清洁能源利用技术。循环流体在地下热储中的流动与换热对EGS的采热性能有重要影响。本文首先对EGS数值模型进行了综合评述，然后基于一套自主开发的三维瞬态数值模型模拟了不同渗流条件下EGS地下热储内的热流过程。通过对模拟结果的分析，揭示了均匀压裂的人工热储中流体短路的形成机理，并通过对比双井和三井系统中流场和局部地热开采率分布，结合当前钻井工艺和裂隙激发技术水平，探讨了抑制流体短路、优化EGS采热性能的可能方案。%Enhanced geothermal system aiming to mine heat from hot dry rocks (HDR) locating within subsurface 3~10 km depths represents a promising renewable energy utilization technology. It normally needs to create an artificial heat reservoir in HDR by a certain rock-fracturing technology such as hydraulic stimulation and then to circulate heat transmission fluids through the heat reservoir to extract heat for earth-surface power-generation utilization. The flow and heat transport process in the subsurface reservoir has significant influence on the heat extraction performance of EGS. A detailed review on EGS numerical models is given first, and then a self-developed 3D transient model focusing on the subsurface thermo-fluidic process in EGS during heat extraction is briefly introduced. With this model, long-term operation processes of EGSs are simulated. Analyzing the simulation results reveals the formation mechanisms of “short circuit”flow in homogeneously fractured reservoir. We then perform a comparison study on the heat extraction performance of doublet and triplet EGSs. Comparing the seepage flow field and heat extraction ratio distribution for EGSs of different borehole layout, in combination of the state-of-the-art of borehole drilling and reservoir stimulation technologies, we further propose some possible strategies to restraining“short circuit”flow and improving the heat extraction performance of EGS.
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