Inverting methods for thermal reservoir evaluation of enhanced geothermal system

Enhanced geothermal system (EGS) is considered as a solution for current energy crisis and environmental pollution; however, thermal reservoir of EGS is difficult to be accurately quantified. In reservoir evaluating processes, it is very hard to precise the unknown reservoir parameters. This paper, through reviewing the disadvantages of EGS reservoir evaluation methods and parameters estimation methods in previous studies, found that the reservoir evaluation based on probability model is inaccurate. It is also found that there is less previous studies on resources evaluation by solving inverse problem of heat conduction, while the used methods for solving inverse heat conduction problem (including Tikhonov regularization, Gradient Optimization and Decentralized Fuzzy Inference) have their drawbacks. Then, we proposed a novel fuzzy inversion model for reservoir evaluation. This three-dimensional fuzzy inverting model, including three main strategies of heat transfer direct problem modeling, inverse problem modeling and experimental validation, is built in terms of thermal physical parameters of reservoir. The fuzzy inversion model is able to compute the entire geothermal field temperature, establish the quantitative relationship between heat storage quantity and reservoir thermal property, and evaluate EGS heat reservoir. The proposed framework in this study can be used as a guidance for geothermal researchers and companies to build an evaluation tool of energy resources of EGS.