Gas- and Liquid-Phase Tracer Testing at the Los Azufres, Mexico, Geothermal Field: Current Status

Abstract

We run two tracer tests in the Maritaro-La Cumbre area of the Los Azufres, Mexico, geothermal field. The objectives were to determine whether the fluids injected in well Az-15 recharge the production area of six production wells; and to estimate the fraction of injected fluid recovered in them, if any. Because only three of these wells produce water and all of them produce steam, two tracers were used, SF6 for the gas phase and 1,3,6 naphthalene trisulfonate for the liquid phase. All the observation wells recorded the gas-phase tracer, and two of the three water-producing wells recorded the liquid-phase tracer, proving that fluids injected in well Az-15 do recharge the area of interest. The liquid phase tracer was not detected in well Az-28 located nearly 2 km away from the injector, most likely due to dilution beyond its detection limit. Because 1,3,6 naphthalene trisulfonate returns are still strong in the wells producing it, it is yet too early to estimate reliable recovery factors for these wells. The (fast) first arrival of the gas-phase tracer was missed in all wells. Because of that, no reliable recovery factors from the gas-phase tracer results will be available from this study.