Copahue Geothermal Field

We characterize the Copahue Geothermal Field and ultimately update its electrical generating capacity values to approximately 10 MWe.

 Summary

In this project we characterized the Copahue Geothermal Field by a detailed structural prospection in the Caldera del Agrio. This geothermal system is located in the province of Neuquén, Argentina, and is the most attractive one from the whole country. Throughout its 50 years of history, the system reached significant milestones, such as being the first powerplant in South America. This project translated into three publications that are summarized below.

 In Barcelona et al. (2019), we propose a compartmentalized reservoir model made up by three fault segmented blocks that ultimately was formed because of the extensional dynamics that prevail in the caldera. Beneath both blocks from the periphery, a pressurized liquid-dominated reservoir prevails. More important though, there is a clay cap that permitted the accumulation of a vapor zone of higher-enthalpy right beneath the town of Copahue. In Barcelona et al. (2020), we performed a discrete fracture network model and a 3D forward strain-stress model of the upper caprock unit (ignimbrite). On one hand, we suggest that the ignimbrite avoids the decompression of the reservoir because it provides the low fractured and low permeability layer that seals the geothermal system. On the other hand, heavily faulted ignimbrite enhance the shallow vapor zone, given its high fracture density and permeability. Finally, in Barcelona et al. (2021), we assessed the electrical generating capacity of the Copahue Geothermal System by a volumetric method as well as a wellhead output calculation. The most remarkable outcome of the paper is our results support less than half (10.2 - 13.5 MWe) of the previously calculated proven power output (30 MWe) that was used to scale the offered tenders to develop a power plant.