Optimization of heat extraction strategies in fault-controlled hydro-geothermal reservoirs

Abstract

Hydrothermal reservoirs commonly exist in association with fault activities. This study discusses the geothermal energy exploitation strategies in a fault-controlled geothermal system based on the Zhacang geothermal field in the northeastern Tibetan Plateau. The influence of well placement (including production depth, injection depth and well distance) and operation parameters (including injection temperature and production backpressure) on the heat production performance are evaluated by coupled thermal–hydraulic numerical modeling. Results indicate that a geothermal energy production of 1.67 MW can be obtained in the Zhacang geothermal field in 50 years, when the injection rate is 2.5 kg/s and injection temperature is 10 °C, with the injection depth at 1500 m, production depth at 300 m and well distance at 300 m. This optimized strategy is weakly affected by the terrestrial heat flux, because the heat transport in permeable fault zone is dominated by convection rather than conduction. Heat production increases with permeability in the conductive fault zone. The relationship between geothermal energy production and the associated natural and anthropogenic factors discussed in this study can help optimize heat extraction management in the other fault-controlled hydro-geothermal reservoirs.