2-D Inversion of DC Resistivity Data from the Cerro Prieto Geothermal Area, Mexico

Abstract

The Cerro Prieto Geothermal area, one of several geothermal areas in Mexico, was the first to be developed and, at the present, it is the largest in the country (620 MW). Because of its importance, many geophysical, geochemical and geohydrological techniques have been applied in order to have a better understanding of the spatial distribution of the reservoir. From the geophysical point of view, DC resistivity and Magnetotelluric methods have demonstrated to be very successful in resolving the spatial distribution of conductivity in the subsurface. With this purpose, several field works have been conducted to collect DC resistivity data. In this way, the Mexican Commission of Electricity (CFE) collected in 1977- 79 more than 411 deep Schlumberger soundings (maximum AB/2= 5 km), arranged in lines. These give us the opportunity to attempt a two-dimensional inversion of such lines. Also, in 1977-79 the Lawrence Berkeley Laboratory collected three long-offset dipolo-dipole lines in the same region (maximum n= 8; a=1 km). We are inverting Schlumberger and dipoledipole data jointly, where possible, or just Schlumberger data. This give us a picture of the main features of the principal reservoir of the Cerro Prieto Geothermal area. This new information is compared with different information available of the whole geothermal area.