Natural Vertical Flow in the Los Azufres, Mexico, Geothermal Reservoir
This work focuses on estimating the mass (M) and energy (E) flow rates, the permeability k, and the relative permeability functions R{sub L} and R{sub V} associated with the natural vertical flow in the reservoir. To estimate M and E we used the standard 1-D vertical equations for two-phase flow, complemented with boundary conditions at the boiling and dew interfaces. These boundary conditions were derived in an earlier stage of this study that established an approximate 1-D vertical model of the reservoir. The estimated values of M and E were then used together with the previously established liquid saturation vertical profile of the reservoir, and the differential equation expressing the pressure gradient, to fit, by trial and error, the observed natural pressure profile. The accuracy of the fit depends on the assumed value for the vertical permeability and on the chosen forms for the relative permeability functions. They estimated M {approx} 6.9 x 10{sup -8} kg m{sup -2} s{sup -1} and E {approx} 0.2 W m{sup -2}. These results lie well within the ample ranges of mass and energy flowrates per unit area found in geothermal fields worldwide. The estimated values of M and E support the previous inference that there is an extensive caprock in the reservoir. The best fit to the natural pressure gradient implies a vertical permeability of about 0.08 mD, residual water- and steam-saturations of about 0.04 and 0.00 respectively, and ''fracture relative permeabilities'' (i.e., R{sub L} + R{sub V} = 1). This work addresses a major obstacle for a successful analysis of the Los Azufres geothermal reservoir, which is characterized by an extensive two-phase region: the former unavailability of reasonably reliable relative permeability functions. Furthermore, the present characterization of the vertical natural flow provides important constraints for both lumped- and distributed-parameter models of the reservoir. Finally, this work gives information on reservoir properties that would be difficult to obtain by other means.
- Research Organization:
- Instituto de Investigaciones Electricas, Cuernavaca, Morelos, Mexico; Comision Federal de Electricidad, Cd. Hidalgo, Michoacan, Mexico
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AS03-80SF11459; AS07-84ID12529
- OSTI ID:
- 887153
- Report Number(s):
- SGP-TR-93-35; TRN: US200618%%162
- Resource Relation:
- Conference: Proceedings, Eleventh Workshop Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 21-23, 1986
- Country of Publication:
- United States
- Language:
- English
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