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Barragán, Rosa María
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- PublicationOpen AccessGas geochemistry for the Los Azufres (Michoacán) geothermal reservoir, México(2005)
; ; ; ; ; ;Barragán, R. M.; Instituto de Investigaciones Eléctricas, Gerencia de Geotermia, Cuernavaca, Morelos., México ;Arellano Gómez, V. M.; Instituto de Investigaciones Eléctricas, Gerencia de Geotermia, Cuernavaca, Morelos., México ;Portugal, E.; Instituto de Investigaciones Eléctricas, Gerencia de Geotermia, Cuernavaca, Morelos., México ;Sandoval, F.; Comisión Federal de Electricidad, Residencia Los Azufres, Campamento Aguafría, Los Azufres, Michoacán, México ;Segovia, N.; Instituto de Geofisica, Universidad Nacional Autónoma de Mexico (UNAM), México D.F., México; ; ; ; Gas data of the Los Azufres geothermal field were analyzed using a method based on equilibrium of the Fischer- Tropsch (FT) reaction: CH4 + 2H2O = 4H2 +CO2 and on the combined pyrite-hematite-magnetite (HSH2) reactions: 5/4 H2 +3/2 FeS2 +3/4 Fe2O3 + 7/4 H2O = 3 H2S +Fe3O4 in order to estimate reservoir temperature and excess steam. The solution of equilibrium equations produces a grid (FT-HSH2). This method is suitable for reservoirs with relatively high H2S but low H2 and NH3 concentrations in the fluid as is the case of the Los Azufres well discharges. Reservoir temperature and reservoir excess steam values were estimated for initial and present conditions in representative wells of the field to study the evolution of fluids, because of exploitation and waste fluids reinjection. This method was very useful in estimating reservoir temperatures in vapor wells, while in two-phase wells it was found that as the well produces a smaller fraction of water, the reservoir temperature estimation agrees qualitatively with results from cationic or silica geothermometers. For liquid-dominated wells the reservoir temperature estimations agree with temperatures obtained from the well simulator WELFLO. This indicates that FT-HSH2 results provide the temperature of the fluid entering the well where the last equilibrium occurs. Results show a decrease in reservoir temperatures in the southern zone of the field where intensive reinjection takes place. With exploitation, it was also noted that the deep liquid phase in the reservoir is changing to two-phase increasing the reservoir steam fraction and the non-condensable gases in well discharges.216 490 - PublicationRestrictedGeochemical characteristics of pore waters from sediment cores of the Wagner Basin, Gulf of California(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Wagner Basin (WB) is a shallow basin (depth < 225 m) belonging to the northernmost section of the Gulf of California rift system. Hydrothermal activity and high heat fluxes prevail in some regions of the WB. For this contribution, we report the first dataset of chemical (major and some trace elements) and isotopic compositions (δ18O, δD, 87Sr/86Sr, δ13C) from pore water sampled at the bottom of the WB, in areas affected by hydrothermal activity. The goals of the study are to determine the origin of the fluids emanating from the anomalous heat flow zones and to characterize the physical and chemical processes controlling their composition. The 18 pore water samples are classified into two groups: low temperature (LT) and high temperature (HT) samples, according to the sampling temperature (from 16.4 to 25.6 °C, and 32.5–99.6 °C, respectively). LT samples have chemical and isotopic (δ18O and δD) compositions similar to those of present-day seawater. On the opposite, HT cores are typically more enriched in Cl (26,100–37,074 mg L−1) and other elements (Br, Na, K, Ca, B and Sr) than those of present-day seawater (Cl = 20,284 mg L−1). HT samples are also strongly depleted in deuterium isotopes (up to −30.48‰). This characteristic could be related to the mixing between ancient evaporated seawater and Colorado river waters. Conceptually, the origin of a saline paleo-aquifer/reservoir can be related with the gradual marine flooding of shallow lagoons and depressions at the time Gulf of California was rifting (6–8 Ma) or during the Last Glacial Maximum (20–26 Ky). Additionally, it is not ruled out that some of the deuterium depletion observed in HT samples may be related to secondary processes (e.g., clays exchange, organic matter). Radiogenic 87Sr/86Sr signatures (0.70929–0.70997) of the HT samples likely reflect the leaching of radiogenic continental sediments from the Colorado River (filling the WB) and authigenic minerals (e.g., calcite or barite) precipitated from seawater. Solute geothermometry indicates that HT pore fluids underwent water-rock interactions at temperature of at least 220 °C. Finally high δ13C values (up to +10.5‰) in DIC from HT samples indicates partial equilibration of methane with DIC, or partial reduction of DIC.215 10