The Geothermal System of ArarÛ, Mexico, as an Independent System of Los Azufres

Abstract

A new interpretation of the exploration results of the ArarÛ, Michoac·n, MÈxico, geothermal zone, and especially from one deep (1344 m) well drilled there, allows us to conclude there is evidence for a geothermal reservoir at this depth. The system seems to be a fracture zone reservoir fed by a deep, narrow conduit related to the ArarÛ-Zimirao fault. It is probably a convection, liquid-dominant system, with sodium chloride fluids, medium to high temperatures (220-250?C), salinity around 3000 ppm as TDS, pressures close to hydrostatic, and low heat loss. The system appears to have been deepened over time by alternating episodes of self-sealing and hydro-fracturing, but still it is possible to expect commercially favorable temperatures and production conditions at depth. As suggested by the geochemical and isotopic data presented, the ArarÛ geothermal system is an independent and genetically different system of the relatively nearby Los Azufres reservoir.