Hydraulic Stimulation Scenarios for a Potential Enhanced Geothermal System (EGS) in Acoculco, Mexico

Abstract

The Acoculco geothermal system, located ~130 km NE of Mexico City, has been accessed in the past decade by the two exploration wells EAC-1 and EAC-2. Despite temperatures of more than 260°C at 2 km depth, the low permeability of the metamorphic, intrusive and hydrothermally altered rocks makes a conventional geothermal development of these wells impossible. The question is whether and how these wells may be stimulated in order to develop an economically viable enhanced geothermal system (EGS). In order to approach this question, field and laboratory data is acquired to setup a parameterized conceptual local geological model, which is the basis for different numerical models. The numerical models are used to simulate a variety of hydraulic stimulation scenarios and evaluate their impact on the reservoir. First, different hydraulic stimulation scenarios are simulated in order to estimate fracture geometries and stimulated reservoir volumes. The resulting fracture geometries are then transferred to a THM reservoir simulator to evaluate the hydraulic performance increase. This study presents the site and provides an outline of the methodology to develop a site-specific development concept for wells EAC-1 and EAC-2 in Acoculco. This will aid the decision making process for the exploitation of the geothermal reservoir, providing answers to whether and how the existing wells can be stimulated or if new wells need to be drilled in more permeable zones of the caldera.