Preliminary Geochemical Model of the Domo San Pedro Geothermal Field in San Pedro Lagunillas, Mexico

Abstract

Domo San Pedro is a magmatic hydrothermal system located in San Pedro Lagunillas, Nayarit. The Domo San Pedro reservoir is a liquid dominated type of reservoir, which is evident in the fact that the pressure and temperature profiles of the wells show that in the reservoir the pressure is hydrostatic, meaning higher than the saturation pressure which makes compressed liquid the prevailing conditions. Also, the wells discharge a mix of brine and steam. The water classification of the field is type sodium chloride, with a neutral or slightly acidic pH. The chloride concentration in the reservoir varies between 850 ppm to 1200 ppm. Brine geothermometer temperatures agree well with downhole surveys and show the field has a temperature between 260°C and 340°C. By combining the chemistry observed from the wells and the warm springs, with a structural geology campaign, a preliminary origin of fluid and flow direction, as well as a geochemical model is presented here.