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增强型地热系统(EGS)旨在经济开采地下3~10 km区域干热岩蕴含的热能,并用于地面发电。EGS经济性与其采热性能直接关联,人工热储内热交换过程是需要重点研究的内容。热储内裂隙形貌及分布对采热过程有重大影响。基于热储裂隙开度和长度的分形特征,本文建立起EGS分形分叉网络模型,推导出EGS采热速率表达式。分析发现泵功、裂隙最大开度、扭曲率分形维数、裂隙开度分布分形维数、裂隙分叉网络级数及裂隙长度都是影响EGS采热速率的重要因素。
The Enhanced Geothermal System (EGS) aims to economically exploit the thermal energy contained in dry-hot rocks in the region 3 to 10 km underground and to generate electricity on the ground. The economy of EGS is directly related to its heat recovery performance, and the heat exchange process in artificial heat storage is the key to be studied. Thermal fractures in the reservoir morphology and distribution of the heat transfer process has a significant impact. Based on the fractal characteristics of the opening and the length of the thermal reservoir, an EGS fractal bifurcation network model was established and the EGS heat rate expression was derived. It is found that the pump work, the maximum opening of fractures, the fractal dimension of distortions, fractal dimension of fractures opening degree, the number of fissure network fractures and the crack length are both important factors affecting the heat recovery rate of EGS.