Lithological correlations of the cerro prieto wells, based on well - log interpretation

This paper presents the results of correlations of the geophysical well logs obtained from wells drilled at the Cerro Prieto geothermal field. From this correlation, a structural interpretation of the ‘receptacle’ holding the geothermal fluids has been obtained.Based on the temperature and electrical resistivity logs, the presence of two main geothermal reservoirs has been established. It was also found that most of the wells were completed such that production is obtained simultaneously from several sandy layers. In all probability this has created some mechanical problems in the wells in addition to a certain confusion in the interpretations based on fluid production data.An hypothesis is postulated about the deposition environment and the genesis of the reservoir, on the basis of which it is concluded that the reservoir is a paleochannel. It is also postulated that thinning of the basement rocks is the fundamental cause of the heat transmission to the reservoirs.Tables listing the correlating marker horizons for each well and maps showing the top of the two main reservoirs and the isopacks for the shallow one are presented. From these data have been inferred the areas showing the best possibilities for immediate geothermal development.