Thermal and Hydrological Regional Characterisation of Los Humeros and Acoculco Using Modelling Methods -H2020 GEMex Project

The GEMex project is a collaborative effort between Mexican and European research institutes to develop the understanding of Enhanced Geothermal Systems (EGS) and SuperHot Geothermal Systems (SHGS). For this purpose, two volcanic sites have been selected: Los Humeros and Acoculco. Both sites are volcanically active or have experienced volcanic activity recently, including caldera formation at some point in their history. In Acoculco, the recently published work of Avellán et al. (2018) show the latest knowledge on the evolution of the volcanic system. In Los Humeros, Carrasco-Núñez et al. (2017) present a reinterpreted history of the whole system. However, while Los Humeros has experienced strong hydrothermal activity, Acoculco is presently considered as a dry system. In the frame of this GEMex project thermal models have been developed for both sites and a hydrothermal model in Los Humeros. The thermal models rely on 3D geological models, also developed in GEMex and information such as rock properties (also being acquired within GEMex) and temperature data (limited in Acoculco and more extensive but regrouped in Los Humeros). In Los Humeros, a fast and efficient thermal modelling methodology was applied, considering the regional heat source and advection related to regional groundwater flow and local high permeability zones. The hydrogeology in Los Humeros has been specifically modelled based on groundwater flow in the limestone basement, taking into consideration the heat source below the volcanic system. In Acoculco, given the scarce temperature information available, work has focused on investigating the geometry of the heat source and the resulting thermal structure. Results from geological and thermal model coupled with petrophysic rocks properties are used for the resources assessment of the two sites. A common computation, based on volume method, was applied on both areas in order to obtain the thermal energy stored in the underground (Heat in Place). A better understanding of the nature of the Los Humeros and Acaculco geothermal systems is key for sustainable and safe production and for future geothermal exploration and development.