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| One of the authors of the study, D. Pinti, collecting noble gases in a copper tube system from a geothermal well (photo credit D. Pinti). |
Mexico is one of the countries that has high-enthalpy geothermal resources. The Federal Electricity Commission of Mexico (CFE, Comision Federal Electricidad) exploits several fields where steam is extracted in deep wells at rates of several tens of tons per hours to generate electricity. For four years, an international team of scientists from Mexico, the USA, and Canada have studied the origin and sources of steam contained in these fields, particularly at Cerro Prieto (Baja California).
Cerro Prieto is the largest high-enthalpy geothermal field exploited for electricity production in the world. After 50 years of exploitation, 429 geothermal wells were drilled. Currently, 147 operating wells extract approximately 34.6 million metric tons of steam per year, for a total installed capacity of 570 MWe, capable of providing the electrical consumption needs of the Baja California state.
Cerro Prieto is the largest high-enthalpy geothermal field exploited for electricity production in the world. After 50 years of exploitation, 429 geothermal wells were drilled. Currently, 147 operating wells extract approximately 34.6 million metric tons of steam per year, for a total installed capacity of 570 MWe, capable of providing the electrical consumption needs of the Baja California state.
Because the total amount of radiogenic 4He in the fluid is proportional to its production rate in the rock, a gross estimate of the fluid residence time can be calculated. Results give water “ages” of 1.5-1.8 million years, which is the age of deposition of deltaic sediments that constitutes the geothermal reservoir of Cerro Prieto. This means that part of the steam produced at Cerro Prieto is as old as the rock which contains it. This discovery put a serious threat on the sustainability of the geothermal resource, as any fossil energy stored in the terrestrial crust. This connate component of fluids needs to be clearly identified and volumes precisely estimated to determine the durability of the resource and for a correct management planning for future exploitation of this energy form.
