Mixing and Dilution Processes at the Las Tres Virgenes (Mexico) Geothermal Reservoir Indicated by 1997-2007 Geochemical Data

Abstract

The Las Tres Vírgenes geothermal field, located in the Baja California Peninsula (México) has currently an installed power capacity of 10 MWe. The reservoir is liquid-dominated with temperatures in the range 250-275°C. In this work we present the results of an investigation of the main physical processes at the Las Tres Vírgenes geothermal reservoir, based on the study of geochemical data for the period 1997-2007. The results indicate the occurrence of mixing and dilution processes between two end members; the characteristic reservoir fluid (average 274°C, Cl concentration of 6,745 ppm), which is typically produced by the deepest well, LV-13 (2,414 m deep), and a lower-temperature end member (171-202°C, Cl concentration of ~500 ppm), that resembles the fluids produced by the shallowest well LV-2 (1,270 m deep). According to this, the fluids discharged by wells LV-1, LV-3, LV-4 and LV-11 over time consist of mixtures of different fractions of these end members. As multiple entries to the wells were also identified, it is likely that fluid mixing occurs in the wells, which strongly promotes mineral scaling in well casings.