A two-dimensional temperature field simulation of the La Primavera geothermal area, México

Abstract

A reasonable estimation of the geothermal potential of any geothermal system depends on the reliable knowledge of its geological, geophysical and geochemical parameters. The heat flow is an important geophysical criterion used to describe the subsurface temperature profiles in prospecting areas. These profiles are helpful tools to locate high temperatures and thermal disturbances (heating or cooling) that could indicate permeable or fractured zones in the subsurface. A good area to apply this approach is the La Primavera caldera (LP), México, with an estimated geothermal potential high enough to install a 75 MW power plant. A conductive model of La Primavera would provide vital information to understand the heat flow during future work on and eventual exploitation of the geothermal field. We developed a 2D conceptualized numerical model of La Primavera based on the heat transfer equations. Then, we applied the Tri-Diagonal Matrix Algorithm (TDMA) method to discretize the equations. The resulting model described the temperature distribution as a function of depth in 10 geothermal wellbores drilled within an area of 4 km2 inside the caldera. The lithology of these exploration wellbores (subsurface stratigraphy) was used to correlate the proposed 2D geological profiles and to construct the model geometry and thermal conductivity at depth. The temperature profiles were used as boundary conditions to calibrate and validate the numerical model. The results indicate that estimated temperatures (450-500 °C) occur at depths of 3 km hosted within the granitic basement beneath La Primavera. These high temperatures may be linked to remnant intrusive bodies located in depth. These results suggest that La Primavera is a promising target for future geothermal exploitation.