Thermal Evolution (1984-2005) of the Los Humeros (Mexico) Geothermal Fluids as Indicated by Chemical Geothermometers*

The thermal evolution of Los Humeros geothermal fluids was estimated by using liquid and gas chemical geothermometers and results indicate two separated fluid entries to the wells: a (∼250°C) liquid produced from a shallower reservoir and a (>300°C) steam produced by a deeper stratum. Both entries were identified by Na/K and SiO2 geothermometers for the liquid and H2/Ar for the steam. CO2/Ar geothermometer seems to provide temperatures of mixed fluids entering the wells. Based on thermal evolution of fluids, multiple fluid entries in wells were characterized while reservoir exploitation-related processes like cooler water entries and condensation phenomena, were also identified.