Theoretical model of geothermal tail water reinjection based on the equivalent flow channel model
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摘要: 深层地热能是一种清洁环保的可再生能源，尾水回灌是深层地热可持续开发利用的重要保证，但目前国内地热尾水回灌还处在起步阶段，地热尾水回灌方案优化设计的理论模型尚不成熟。文章结合示踪试验，提出了基于等效渗流通道模型的热储参数反演与开采井热突破预测的完整理论框架。应用多孔介质溶质运移理论，修正了等效渗流通道中的溶质浓度解析解，并联合移动渐近线法提出了热储参数反演理论模型；推导了等效渗流通道中的对流传热解析模型，可对开采井中的水温变化进行预测。依托山东省德州市平原县魏庄社区地热对井示踪试验，应用该理论框架进行了示踪试验反演及开采井热突破预测，并对影响开采井热突破的主要因素进行了敏感性分析。Abstract: Deep geothermal resources are clean, environmentally friendly and renewable, and geothermal tail water reinjection plays an important role in the sustainable management of deep geothermal reservoirs. However, the progress of geothermal tail water reinjection is slow in China, and theoretical models guiding geothermal tail water reinjection is still under development. Based on tracer tests and equivalent flow channel models, this study proposes a theoretical modeling framework in order to back-calculate the unknown parameters of geothermal reservoirs and predict the thermal breakthrough in the production well. The inverse modeling module combines the analytical solution of the tracer transport equation with the method of moving asymptotes, and an analytical model considering heat advection and transfer can be used to predict the thermal breakthrough in the production well. Based on the results of tracer tests in the double geothermal wells near Dezhou of Shandong, two equivalent flow channels were determined and their average flow velocity, dispersion coefficient, section area and channel length are estimated by using this theoretical framework. The possible thermal breakthrough in the production well and its main influencing factors are also discussed.
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Key words:
- tail water reinjection /
- sandstone reservoir /
- tracer test /
- inverse modelling /
- thermal breakthrough
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