Magmatic intrusions drive fluid convection in high-enthalpy geothermal systems, yet industry-standard geothermal reservoir models represent these heat sources using fixed boundary conditions at the bottom of the model domain. This oversimplification ignores the complex heat transfer dynamics between magmatic intrusions and surrounding groundwater. This study presents the first field-scale geothermal model incorporating a discrete magmatic intrusion into the model domain, using the Krafla geothermal system in Iceland as a case study. Krafla offers unique insights with direct evidence from wells drilled into magma. The model is calibrated using the natural state temperature and fluid pressure distribution, as well as production data from the Iceland Deep Drilling Project (IDDP-1) well discharge, which encountered magma at ~2 km depth. Results indicate very high permeability near the magma chamber, which results in steep temperature gradients at the magma-hydrothermal interface and conductive heat fluxes of up to ~24 W/m². Moreover, our model shows how the large-scale thermal structure of the system, including at the depths of conventional production wells, depends on the permeability structure and heat transfer dynamics near the magma-hydrothermal interface. Despite the remaining challenges in imaging subsurface magma bodies and reconstructing complex, time-dependent magmatic histories, our findings suggest that including magmatic intrusions into reservoir models provides novel insights into the thermal structure of magma-driven geothermal systems.

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