Patterns of Change in Water Isotopes from the Cerro Prieto Geothermal Field, Baja California, Mexico: 1977-1986

Abstract

Isotopic analyses of Cerro Prieto well after collected over the last 10 years indicated continued drawdown of cooler, isotopically lighter water from the side and above the reservoir has been most pronounced along a north striking normal fault that intersects the shallow reservoir in the western part of the geothermal field. Hot geothermal fluid recharges the system form the northeast, rising through a major normal fault zone and moving out into the surrounding permeable reservoir. In the central region of the field, near the reservoir boundary, a natural region of two phase fluid exists between the reservoir and the deep reservoir. Comparison ob observed isotopic fractionation between steam and water from production separators on Cerro Prieto wells with experimental fractionation factors indicates steam contamination of most water samples.