Analytical solution for temperature-depth in geothermal reservoirs with mixed heat conduction types: A case study from the Huainan Coalfield, Anhui Province, China

Abstract

Temperature measurements in geothermal reservoirs plays a crucial role in understanding the source of subsurface thermal energy storage and the extraction of geothermal power. However, deploying a multitude of monitoring points during underground drilling results in substantial measurement expenses. To address this challenge, a simplified analytical model is often utilized to estimate the temperature distribution throughout the formation. This estimation relies on wellhead and bottom-hole temperatures, as well as parameters related to the formation's thermal properties. Nevertheless, the varying distribution of groundwater across different zones alters the heat transfer process. Temperature calculations considering multiple transfer processes are still limited. Therefore, in this paper we first formulate two common types of heat transfer models: conduction and convection-conduction. By integrating these two types of heat transfer, we characterize and calculate the temperature distribution for geothermal reservoirs in a manner more aligned with reservoir conditions. To validate the model's accuracy, we compare its calculated results with temperature measurements obtained from geothermal wells in Huainan Coalfield. The results demonstrate that the developed model is highly applicable and exhibits strong simulation accuracy, with the maximum error between the analytical solutions and the measured temperature curve being less than 0.5 °C. This model is particularly suitable for capturing the actual heat transfer behavior in the geothermal reservoir as geothermal water ascends. Furthermore, it can be employed to invert the volume flow rate of geothermal water, highlighting its significance in geothermal development engineering.