| Title | Fluid-Mineral Equilibrium of Spring Waters at Cuitzeo Basin (Mexico) Geothermal Zone |
|---|---|
| Authors | Nuria Segovia, Rosa María Barragán, Ruth Alfaro, Víctor M. Arellano, Manuel Mena |
| Year | 2010 |
| Conference | World Geothermal Congress |
| Keywords | fluid-mineral equilibrium, reservoir temperature, saturation indices, Cuitzeo Basin, Mexico, geothermal springs |
| Abstract | In this work fluid-mineral equilibrium for six spring waters from Cuitzeo Basin geothermal zone for a range of temperatures was studied in order to investigate the temperature/s at which it was attained and by this approach, to estimate the reservoir temperature. The results of both the chemical speciation and the saturation indices of hydrothermal minerals were obtained from the chemical composition of spring waters as input data by using the REACT routine of the Geochemist Workbench (GWB) program for a wide range of temperatures (from sampling temperature to 300C). Suitable plots of saturation indices vs temperature were developed by using the GTPLOT routine of GWB. As an example, the results for one spring with a sampling temperature of 75C are given. For this sample the fluid-mineral equilibrium results indicated not only one temperature since saturation indices of some minerals tended to converge each other at the cero value at 240-260C; 180-200C and 140-150C. These results partially agreed with reservoir temperature estimations obtained by chemical geothermometers which provided the following results: T Na/K between 132 and 146C and T SiO2 between 188 and 194C (depending on the expression used). As no chemical geothermometers provided temperatures as high as 250C for the reservoir, it is suggested that cooling processes of the original fluid take place by mixing with shallower, lower temperature waters when the fluid flows to the surface. These results are useful to support exploration and development activities at Cuitzeo Basin zone to make use of the resources for power generation and/or direct applications. |