Cerro Prieto Uno Area in Cerro Prieto Field Mexico Through 30 Years of Commercial Production

Abstract

The first area under exploitation in Cerro Prieto
geothermal field in MÈxico was Cerro Prieto I, this
area of 4.5 km 2 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. As a consequence of the cooler
recharge some production wells in this area show
temperatures decreasing higher than 50 ?C, and other
show reversal temperatures in the downhole, besides
the cold water inflow has been affecting the steam
flow rate production of the wells, the number of
production wells in this area diminished from 43 in
1991 to 20 in 2003. This paper shows and discusses
the actual condition and evolution of the production
area and power plant in Cerro Prieto I.