Cold water injection near the magmatic heat source can enhance production from high-enthalpy geothermal fields

Abstract

Although existing deep geothermal wells have confirmed that shallow magmatic intrusions heat circulating hydrothermal fluids to supercritical temperatures, successfully utilizing such fluids for power generation has proven challenging. As an alternative, using deep geothermal wells drilled into the vicinity of intrusions for injection rather than production has the potential to enhance heat extraction from the intrusion, while simultaneously providing fluid pressure support to the overlying geothermal system. However, the dynamic response of the heat source and overlying geothermal system to deep injection has not previously been investigated using numerical modelling. Here, we present numerical models showing that injection in the near-vicinity of a magmatic heat source increases the production potential of shallower geothermal wells. By locally cooling the hot rock near an intrusion, deep injection increases permeability and the rate of heat transfer across the brittle–ductile transition. The injected fluids ascend in upflow zones above the heat source and provide pressure support to shallower geothermal wells, without significantly affecting the temperature and enthalpy of produced fluids. We investigate a variety of scenarios involving only a single deep injector and a single shallower producer. Our models suggest that deep injection could increase the production potential of shallower geothermal wells by up to 10 percent after 30 years of well operation and by 20 percent after theoretical 100 years, with the magnitude of the impact increasing with continued injection over longer timescales.