| Abstract |
The first area under exploitation in Cerro Prieto geothermal field in MÈxico was Cerro Prieto I, this area of 12 km2 is located in the west part of the geothermal field; it started the commercial production in 1973. Two reservoirs have been identified in CPI area, the shallow alpha and the deeper beta reservoir, which extends over the entire field. Through 30 years under exploitation the old field of Cerro Prieto I have been produced around 800 millions of tons of water-steam mixture; this geothermal area has been showing several reservoir changes in their chemical and thermodynamics properties. This part of the Cerro Prieto geothermal systems is strongly influenced by nearby groundwater aquifers; cooler water readily recharges the reservoir. In response to exploitation, the natural influx of cold water into the shallower alpha reservoir is mainly from the west and possibly from down fault named L, whiles the recharge to the deeper beta reservoir in this part of the field, and seems to be only lateral, from the west and possible south. As consequence of the cooler recharge some production wells in this area show a temperatures higher than 50 ?C, and other show reversal temperatures in the downhole. This paper analysed and discusses the downhole temperatures evolution in this old area of the Cerro Prieto geothermal system with more than 30 years of commercial exploitation |