The Hyrdogeologic-Geochchemical Model of Cerro Prieto Revisted

Abstract

As the exploitation of the Cerro Prieto, Mexico. geothermal field continues, there is increasing evidence that the hydrogeologic model developed by Halfman et al. (1984, 1986) presents the basic features controlling the movement of geothermal fluids in the system. At the present time the total installed capacity at Cem Prieto is 620 MWe requiring the production of more than 10~00 tonnes/hr of a brine-steam miXttm. This significant rate of fluid production has resulted in changes in reservoir thermodynamic conditions and in the chemistry of the produced fluids. After reviewing the hydrogeologic-geochemical model of Cerro Prieto, some of the changes observed in the field due to its exploitation are discussed and interpreted on the basis of the model.