Impact of well placement and flow rate on production efficiency and stress field in the fractured geothermal reservoirs

Geothermal energy has gained wide attention as a renewable alternative for mitigating greenhouse gas emissions. The advancements in enhanced geothermal system technology have enabled the exploitation of previously inaccessible geothermal resources. However, the extraction of geothermal energy from deep reservoirs poses many challenges due to high-temperature and high-geostress conditions. These factors can significantly impact the surrounding rock and its fracture formation. A comprehensive understanding of the thermal–hydraulic–mechanical (THM) coupling effect is crucial to the safe and efficient exploitation of geothermal resources. This study presented a THM coupling numerical model for the geothermal reservoir of the Yangbajing geothermal system. This proposed model investigated the geothermal exploitation performance and the stress distribution within the reservoir under various combinations of geothermal wells and mass flow rates. The geothermal system performance was evaluated by the criteria of outlet temperature and geothermal productivity. The results indicate that the longer distance between wells can increase the outlet temperature of production wells and improve extraction efficiency in the short term. In contrast, the shorter distance between wells can reduce the heat exchange area and thus mitigate the impact on the reservoir stress. A larger mass flow rate is conducive to the production capacity enhancement of the geothermal system and, in turn causes a wider range of stress disturbance. These findings provide valuable insights into the optimization of geothermal energy extraction while considering reservoir safety and long-term sustainability. This study deepens the understanding of the THM coupling effects in geothermal systems and provides an efficient and environmentally friendly strategy for a geothermal energy system.