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Instituto de Geofisica, Universidad Nacional Autónoma de Mexico (UNAM), México D.F., México
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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 - PublicationOpen AccessRadon, water chemistry and pollution check by volatile organic compounds in springs around Popocatepetl volcano, Mexico(2005)
; ; ; ; ; ; ; ;Segovia, N.; Instituto de Geofisica, Universidad Nacional Autónoma de Mexico (UNAM), México D.F., México ;Peña, P.; Instituto Nacional de Investigaciones Nucleares (ININ), México D.F., México ;Valdés, C.; Instituto de Geofisica, Universidad Nacional Autónoma de Mexico (UNAM), México D.F., México ;Armienta, M. A.; Instituto de Geofisica, Universidad Nacional Autónoma de Mexico (UNAM), México D.F., México ;Lopez, B.; Instituto Nacional de Investigaciones Nucleares (ININ), México D.F., México ;Cisniega, G.; Instituto Nacional de Investigaciones Nucleares (ININ), México D.F., México ;Mena, M.; Instituto de Geofisica, Universidad Nacional Autónoma de Mexico (UNAM), México D.F., México; ; ; ; ; ; Popocatepetl volcano is a high-risk active volcano in Central Mexico where the highest population density in the country is settled. Radon in the soil and groundwater together with water chemistry from samples of nearby springs were analysed as a function of the 2002-2003 volcanic activity. The measurements of soil radon indicated fluctuations related to both the meteorological and sporadic explosive events. Groundwater radon showed essential differences in concentration due to the specific characteristics of the studied springs. Water chemistry showed also stability along the monitoring period. No anthropogenic pollution from Volatile Organic Compounds (VOCs) was observed. An overview of the soil radon behaviour as a function of the volcanic activity in the period 1994-2002 is also discussed.172 501 - PublicationOpen AccessWater chemistry and soil radon survey at the Poas volcano (Costa Rica)(2005)
; ; ; ; ; ;Barquero, J.; Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Heredia, Costa Rica ;Fernandez, E.; Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Heredia, Costa Rica ;Monnin, M.; Hydrosciences, Université Montpellier 2 (UM2) - CNRS, Montpellier, France ;Seidel, J. L.; Hydrosciences, Université Montpellier 2 (UM2) - CNRS, Montpellier, France ;Segovia, N.; Instituto Nacional de Investigaciones Nucleares (ININ), México D.F., México; ; ; ; Radon-in-soil monitoring at the Poas volcano (Costa Rica) has been performed together with water chemistry from the hot crater lake since 1981 and 1983 respectively. The results are discussed as a function of the eruptive evolution of the volcano over a 13 years period (1981-1994). It is shown that no definitely clear precursory radon signals have been recorded. On the contrary, ionic species concentrations are likely to be considered good precursors, together with the temperature variations of the crater lake water.150 210