Prediction of the Temperature Regime of an Underground Collector in a Geothermal Circulation-Based Heating System

The results of a numerical study of the temperature regime of a geothermal field formation are presented. A mathematical model of the heat exchange process between geothermal fluid and rock has been developed. The model of geothermal fluid movement consists of a system of continuity, momentum, and energy equations. At the beginning of computer modeling, the geometry, system parameters, as well as initial and boundary conditions are defined. Water injection technology maintains reservoir pressure and high flow rates, but leads to a decrease in temperature in the aquifer. Reducing the temperature of the geothermal fluid is a crucial issue for long-term operation, the prediction of which is possible with the help of computer modeling. The cooling of the formation is determined by the position of the cooling front, which is defined by an isotherm with a temperature of 288 K. The solution has been obtained by computer modeling. It has been shown that the displacement of the formation cooling front is determined by the thermophysical properties of the rock formations, filtration rate, physical properties of the geothermal fluid, and the temperature of the geothermal fluid supplied to the injection well. The relationship governing the displacement of the formation cooling front has been obtained. The cooling of the formation depends on the distance between the production and injection wells of geothermal fluid and the pressure drop in the formation. The significant influence of the flow rate of the wells has been shown. With a flow rate of 10 m3 /h over an operating period of 7500 hours, the temperature of the geothermal fluid is predicted to decrease from 347 K to 338 K; with an increase in flow rate to 100 m3 /h, a decrease in temperature from 347 K to 325 K is possible. It has been shown that the cooling of the formation mainly occurs in the horizontal plane. Comparison of obtained numerical data with known literature has been performed. Extending the operational lifespan is possible through the implementation of the periodic short-term operation-stop technology (a 10-year cycle, totaling 100 years). This technology allows for greater heat extraction compared to longer-term operation (a 50-year cycle, totaling 100 years).Additionally, increasing the distance between production and injection wells to 1000-1500 meters reduces cooling rates and prolongs the lifespan of the geothermal system. When forecasting the temperature regime of geothermal reservoirs, it is necessary to monitor and refine mathematical models with operational and well research data.