A natural state model in TOUGH2 for the Las Tres Virgenes geothermal field, Baja California Sur, Mexico

The availability of geothermal resources in Baja California has been thoroughly documented in the past. This region currently experiences a deficit in electricity production and it is, to date, disconnected from the National Electric Grid. It is therefore essential to provide strategies for a sustainable production of geothermal electricity in this region that besides, contributes to the increasing need for decarbonization of electricity industry. Here we propose an updated conceptual model of the Las Tres Virgenes hydrothermal system, a currently exploited geothermal area that has been active for more than two decades. The objective of this model is to provide thermal and aquifer relationships that gave rise to this system in its natural state. To achieve this, an updated structural model is presented based on recent geological interpretations of the area. Geochemical and geophysical evidences are also integrated in a conceptual model. A detailed pre-processing step of geological data is incorporated to preserve as much as possible the critical field evidences in the discrete model. Numerical simulations are then conducted using TOUGH2 and the equation of state for water and air (EOS3). As a result, the geothermal field is conceived, and numerically validated, as a fault-hosted fossil aquifer. The upflow that feeds the reservoir interacts with a network of faults. Since the faults hosting the aquifer belong to the regional structural feature of Santa Rosalia Basin, it is imperative to deepen the study of these system with regard to their storativity and permeability since they may control the fate of the system in the long term. •A revised conceptual model of a currently operating geothermal field in Mexico.•High resolution grids to represent geological structures.•TOUGH2 natural state simulations in a fault-controlled hydrothermal system.