Borehole observation-based in situ stress state estimation of the Los Humeros geothermal field (Mexico)

In this study, we present results of an in situ stress state estimation for the Los Humeros geothermal field (Mexico) located in the eastern section of the Trans-Mexican Volcanic Belt. During more than 40 years of geothermal energy production, issues related to induced seismicity, reservoir depletion, subsidence, and wellbore stability have occurred in Los Humeros. The in situ stress tensor, being one of the major controls on the above-mentioned phenomena, remains highly uncertain. The high temperatures of the geothermal reservoir at Los Humeros, often exceeding the critical point of water, promote difficulties in performing in situ stress measurements. In this study, based on data commonly acquired from drilling operations from eleven high-temperature wells within the Los Humeros caldera, we constrain the in situ stress state of the geothermal field. For this purpose, we employ borehole observations including borehole breakouts, instances of fluid circulation loss, and injection tests. Results from this study indicate predominantly strike-slip regime with a strong reverse component and NE-SW acting maximum horizontal stress. Utilizing slip and dilation tendency analysis, permeability and seismic activity of major fault zones within the geothermal field could be aptly explained by the acting stress regime. The outcome of this study provides valuable insights into the in situ stress state of the Los Humeros caldera and supports the exploration of conventional and unconventional (i.e., supercritical) geothermal resources.