The increasing interest in hydrothermal systems derives from the required development of renewable energies. Low-enthalpy shallow hydrothermal energy represents an attractive source of heat. For this reason, the number of installations has been continuously rising for the past 15 years. High-enthalpy environments are still underexploited as drilling in deep and hot reservoirs is technologically challenging. Nevertheless, the economic returns of these systems are such that their exploitation will probably develop in the next years. High-enthalpy, convection dominated hydrothermal systems preferentially develop at active plate margins where active tectonics and volcanism are commonly found. In such environment faults have a major control on fluid flow. The behaviour of these faults is however difficult to predict due to their spatially variable structure and permeability. The role of faults on the flow is strongly controlled by their hydraulic properties with respect to those of the host rocks. If faults have lower permeability than the host rocks, they act as barrier to the flow and can seal reservoirs. Vice versa, when host rocks have a lower permeability, faults can act as conduits focusing fluid flow. Assessing the permeability of fault zones is challenging due to the lack of in situ measurements and require thus complementary methods. In the last decade, electrical resistivity tomography (ERT), combined with other fluid data (e.g. temperature and CO2 concentration), has been employed to identify and image the geometry of shallow hydrothermal systems. This method relies on the measurement of the subsurface electrical resistivity and allows the identification of regions where fluids are focused. Complementary numerical simulations of fluid flow are required to constrain the petrophysical properties of the host rocks. Over the past decades, several powerful numerical codes have been developed for the simulation and quantification of fluid flow in the upper crust. However, most of these codes either have a complex structure or lack some flexibility for meshing and the characterization of fluid properties. A new user-friendly and more accessible (e.g. MATLAB based) code is required for both industry and academic purpose.
The goal of NERUDA is to deepen our understanding of high-enthalpy hydrothermal systems by combining numerical simulations of fluid flow with temperature, soil CO2 and deep geoelectrical measurements. The main scientific objective of NERUDA is the development of a geothermal module in the MATLAB Reservoir Simulation Toolbox (MRST), an open-access software for the simulation of fluid flow in reservoirs developed by SINTEF, Oslo, Norway. This module is expected to have a large impact on the scientific community both in academia and in the industry for the simulation of geothermal problems. The second important scientific contribution is to document the tectonic control of a the Tolhuaca hydrothermal system combining geophysical data with temperature, CO2 flux measurements and structural data to propose an evolution model for the hydrothermal system. The collected data will bring further constrains for the exploration of the area that is investigated for geothermal activities by a local company. Generally, NERUDA will deepen our understanding of the tectonic control of high-enthalpy hydrothermal systems, which is also relevant for the exploitation of geothermal energy in Europe.
