Optimization of reinjection well placement in the fault-controlled hydrothermal system using numerical simulation

Abstract Geothermal tail water reinjection is an effective measure to maintain the sustainable production of geothermal resources and prevent the problems of geological environment. In order to avoid excessive thermal breakthrough and pressure drop of the geothermal reservoir, it is very necessary to optimize the distance between the production and reinjection wells. Here in this work, based on the conceptual model of hydrothermal genesis in Yanggao-Tianzhen Basin, a fault-controlled hydrothermal system, optimization of reinjection well placement has been conducted by using numerical simulation which incorporates all the geological and physical processes. Considering the different distance and upstream and downstream positions of production and reinjection wells, the temperature field evolution of the geothermal reservoir and the water pressure evolution in the production well were compared under each case condition. The temperature field evolution revealed that the shorter distance between production and injection wells, the faster the thermal breakthrough. When the reinjection well is located in the upstream of the production well, the thermal breakthrough will be faster than in the downstream. The water pressure evolution in the production well showed that the water level of the production well decreased insignificantly during the simulation time. It is found that the reservoir pressure can be basically maintained conditional on the whole geothermal tail water is reinjected. Based on the above research results, it is better to place the reinjection well at 1km in downstream of the production well. The findings are helpful for the sustainable exploitation of geothermal reservoir.