Regional resource assessment and geothermal models

Both Acoculco and Los Humeros belong to the CFE (Comision Federal de Electricidad) under licencing for geothermal purposes. Los Humeros is a well-developed site with 65 wells drilled and has been producing electricity from Geothermal energy since 1991 and currently has an installed capacity of 94 MW. Los Humeros has been selected to be investigated in GEMex as a Super Hot Geothermal System (SHGS) with temperatures recorded in excess of 380oC. Acoculco is at the exploration stage with two wells drilled close to each other in 1994 and 2008. The system is dry with no major fluid circulation identified so far but with a fairly high temperature of over 300oC at around 2 km. Acoculco is the EGS site of the GEMex project with a high potential to be developed in the future. The work presented in this report is investigating the thermal state of the subsurface at regional scale and associated resources available. To do so, the work has been performed by two teams, Utrecht University was responsible for the investigation of Los Humeros and CNR for Acoculco. The regional understanding of the considered sites is of great importance as it (1) provides boundary conditions for the more local thermal investigation of WP 6 and (2) allows to understand the processes and properties that define these two geothermal regions. Both teams used numerical models to study the emplacement conditions of the main heat source and used the same volumetric method to estimate the heat-in-place. The distinct geological and hydrothermal conditions as well as the data availability for the two fields, has led to two different modelling strategies being applied. The outcome of the thermal structure in the two sites is based first of all on a detailed geological understanding provided by both the European and Mexican team in WP4 and the geological modelling work of the BRGM and CNR in Task 3.1 (WP3) under a join EU-Mexico collaborative workflow. WP6 have provided petrophysical information making the model more accurate and the Mexican Hydrogeological team have provided vital information to understand the regional flow. As a result of this work, we provide two state-of-the-art of the regional (hydro)thermal models based on all parameters concerning the heat source and fluid transport in both Acoculco and Los Humeros