Theoretical model of geothermal tail water reinjection based on the equivalent flow channel model

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.