Heterogeneity of the Liquid Phase, and Vapor Separation in Los Azufres (Mexico) Geothermal Reservoir
Data of chemical and isotopic composition of fluids from Los Azufres geothermal wells is interpreted in order to characterize the composition of the liquid phase, and to define the relation between this phase and fluids from steam-producing wells. Chemical and specific enthalpy data show that most wells considered are fed a mixture of steam and liquid. Thus, flashing occurs in the formation. This poses a problem on the interpretation of isotopic data, because the composition of the feeding mixture need not be representative of the composition of the liquid phase in the reservoir. Two extreme alternatives for the interpretation of isotopic data are considered. In the first alternative the composition of the total discharge is considered to be the same as that of the liquid in the reservoir. In the second alternative the feeding fluid is considered to be a mixture of the liquid phase in the reservoir and the calculated fraction of steam. In addition, this steam is assumed to separate from a much larger mass of that liquid phase at the downhole temperature. The contribution of steam is then subtracted from the total discharge to yield the composition of the liquid phase. Using data for silica concentration in total discharge and separated water, the chloride concentration in the reservoir liquid is calculated. This result is used to calculate the fraction of steam in the feeding mixture of each well. The isotopic data is then corrected as proposed for the second alternative, to yield the composition of the liquid phase. Comparison of the corrected and uncorrected isotopic values shows that the correction has an important effect only when the steam mass fraction in the feeding mixture is large (> 20%). The correction tends to reduce the dispersion of data points in a {delta} D vs {delta}{sup 18}O diagram. Points representing composition of liquid phase show an approximately linear distribution, suggesting a process of mixing of two fluids. Available data appears to rule out the possibility of mixture with local meteoric or shallow ground waters. Some spatial correlations of composition are noted. The composition of fluids produced by two steam wells corresponds to steam separated from a much larger mass of liquid. Temporal variations in the composition of fluid produced by steam well A-6 suggests that this well might be fed with steam from more than one section in the reservoir.
- Research Organization:
- Instituto de Investigaciones Electricas, Cuernavaca, Morelos 62000, Mexico.; Subgerencia de Estudios; Coordinadora Ejecutiva de Los Azufres, Gerencia de Proyectos Geotermoelectricos, Comision Federal de Electricidad
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- AT03-80SF11459
- OSTI ID:
- 889702
- Report Number(s):
- SGP-TR-74-32; TRN: US200620%%139
- Resource Relation:
- Conference: Proceedings, Ninth Workshop Geothermal Reservoir Engineering, Stanford University, Stanford Calif., December 13-15, 1983
- Country of Publication:
- United States
- Language:
- English
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