Thermo-hydraulic 3D modelling, multicomponent geothermometry and stochastic simulations integrated to assess geothermal potential and uncertainty in volcanic environments: insights from La Palma (Canary Islands)

The island of La Palma, in the Canary Archipelago, hosts one of the most promising geothermal prospects in the Atlantic Ocean, linked to the active volcanic complex of Cumbre Vieja. The western sector of this edifice, encompassing the L1 geothermal anomaly, exhibits a high-enthalpy system previously inferred from the integrated data of geophysical surveys and geothermometry. This study presents a preliminary assessment of the electric power generation potential of the L1 reservoir in pre-exploratory conditions, integrating multidisciplinary data sets including 3D magnetotelluric inversion, ambient noise tomography and attenuation tomography, geodetic modelling, and multicomponent solute geothermometry.

A conceptual model of the L1 geothermal system was established and implemented in a 3D thermo-hydraulic simulation using the TOUGH2 code to evaluate the performance of a single-flash power plant supported by 21 deep wells (14 production and 7 reinjection). The geometry of the geological formations was constructed using GeoModeller, integrating available lithological data, stratigraphic information from water gallery excavations, and structural interpretations based on geophysical surveys. The model simulated multiphase flow and heat transport in porous and fractured volcanic media associated with the L1 anomaly. The simulations were implemented using the EOS1 equation of state, which accounts for water and steam as the only active phases, using variable density to enable convection. The simulations reproduced the natural steady-state conditions, used as input for the exploitation simulations. Uncertain reservoir and operational variables such as physical and hydraulic parameters of the reservoir and surface geological units were accounted and constrained through Monte Carlo stochastic simulations (100 realisations) over a 90-year production period. The simulations yielded expected net electric power outputs ranging from 23 to 45 MWe, with a median value of approximately 36 MWe, a P90 conservative estimate of 31 MWe, and a P10 optimistic scenario of 42 MWe.

The results highlight a stable, convective reservoir with temperatures of 213–231 °C at depths of 2.4–2.7 km, capable of sustaining long-term energy extraction with minimal thermal decline. These findings indicate that the L1 system represents a viable medium-to-high-enthalpy resource comparable to other productive basaltic geothermal fields worldwide. The development of this resource could significantly advance renewable energy transition in La Palma, reducing dependence on fossil fuels and contributing to the pathway toward carbon neutrality.