First Geochemical Data from Cerro Pabellon Geothermal Project (Apacheta Region, Chile)

Abstract

Cerro Pabellón (Chile) is the newly developed geothermal field by Geotermica del Norte (GDN) and it is the first under production in South America. It is located in ‘Pampa Apacheta at 4500 m a.s.l.’. No surface manifestations indicate the presence of a deep liquid geothermal resource at high enthalpy (250°-260°C). A shallow borehole (187 m depth) drilled by Codelco (Corporación Nacional del Cobre, Chile) for water research found steam g (at 88°C due to the high elevation) instead of a cold water aquifer. In 2002, the exploration mining lease (330 km2) was assigned to Geotérmica del Norte (GDN). From 2009 to 2017, thirteen wells were drilled to explore the field. All the productive wells found permeability in the geothermal reservoir, hosted in volcanic products. To the present knowledge, the geothermal system is hosted in a graben structure (Apacheta graben) bounded by two NW-SE oriented faults. The geothermal reservoir is liquid dominated and the fluid shows very low gas content. Fluid samples depict a mature system with a chemistry typical of a volcanic-hosted field. Geothermometers indicate apparent temperature equilibrium in the range of 280°-290°C, as compared to 255°C measured in wells, indicating higher temperatures may possibly be found deeper in the system.