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Title: Los Azufres geothermal field: Observed response after 12-year exploitation

Abstract

Exploitation of the Los Azufres Geothermal field was initiated in August 1982, with the electric power generation of five 5-MW wellhead units. Since then another 70 MW have been installed. A large amount of information has been compiled, including geologic, geochemical, production, and reservoir characteristics. The data were evaluated to detect the extent of observable changes in the main reservoir parameters over the twelve-year production period. Pressure and temperature measurements in Los Azufres wells show that geothermal fluid distribution is strongly influenced by the presence of permeable structures. Wellhead production and chemical analysis of the separated brine show that we are dealing with a highly heterogeneous reservoir, were the drawdown and enthalpy changes depend on the position of the well being studied.

Authors:
 [1]
  1. Comision Federal De Electricidad, Los Azufres (Mexico)
Publication Date:
OSTI Identifier:
177298
Report Number(s):
CONF-951037-
TRN: 95:008065-0069
Resource Type:
Conference
Resource Relation:
Conference: Annual meeting of the Geothermal Resources Council, Reno, NV (United States), 8-11 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of Accomplishments of the past and challenges of the future. Transactions, Volume 19; PB: 604 p.
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GEOTHERMAL RESOURCES; RESOURCE EXPLOITATION; MEXICO; GEOTHERMAL FIELDS; ELECTRIC POWER; PRODUCTION

Citation Formats

Maldonado, G.J. Los Azufres geothermal field: Observed response after 12-year exploitation. United States: N. p., 1995. Web.
Maldonado, G.J. Los Azufres geothermal field: Observed response after 12-year exploitation. United States.
Maldonado, G.J. 1995. "Los Azufres geothermal field: Observed response after 12-year exploitation". United States. doi:.
@article{osti_177298,
title = {Los Azufres geothermal field: Observed response after 12-year exploitation},
author = {Maldonado, G.J.},
abstractNote = {Exploitation of the Los Azufres Geothermal field was initiated in August 1982, with the electric power generation of five 5-MW wellhead units. Since then another 70 MW have been installed. A large amount of information has been compiled, including geologic, geochemical, production, and reservoir characteristics. The data were evaluated to detect the extent of observable changes in the main reservoir parameters over the twelve-year production period. Pressure and temperature measurements in Los Azufres wells show that geothermal fluid distribution is strongly influenced by the presence of permeable structures. Wellhead production and chemical analysis of the separated brine show that we are dealing with a highly heterogeneous reservoir, were the drawdown and enthalpy changes depend on the position of the well being studied.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1995,
month =
}

Conference:
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  • Production and chemical data have been compiled and analyzed on a six-month averaged basis for the first four years of electric energy generation with five 5-MW wellhead generators at the Los Azufres geothermal field. The data were evaluated with respect to the extent of observable thermal drawdown of the reservoir from 25 MW of generation in relation to the estimated capacity of the field of several hundred megawatts of power. The analysis updates the previous one compiled after the first two years of continuous production, at which time the results indicated that differences in reservoir temperature estimated from geochemical thermometersmore » and wellhead production data were not statistically significant based on the number of data and the standard deviations. Analysis of the data after four years of operation were made for the larger number of data and smaller standard deviations. The results review the adequacy of the sampling frequency and the reliability of the measurements from statistical t-Test of the means of the first and second two-year periods. 3 figs., 5 tabs., 20 refs.« less
  • All Wairakei well measurements have been reviewed and re-interpreted. In its natural state the field contained a liquid-dominated two-phase zone over a deeper liquid reservoir. The initial pressure distribution was about 10% above hydrostatic, the excess gradient driving the natural discharge. With exploitation and falling pressures, the two-phase zone expanded downwards, and within it a vapor-dominated zone developed. The changes with exploitation can be characterized by two pressures: a deep liquid pressure, reflecting mainly the reservoir mass balance, and a pressure in the stem zone, reflecting the reservoir heat balance. The heat balance indicates that most, but not all, ofmore » the recharge is hot water. Production from wells is currently declining due to falling temperatures and pressures in both zones of the field. The liquid-dominated zone pressure can be raised by reinjection. Deep peripheral injection is estimated to have a payback time of about two years.« less
  • The Kawerau geothermal field is similar to other gas-rich, high temperature systems found in the Taupo Volcanic Zone of New Zealand. The field is situated over a long-lived volcanic centre, where > km of eruptives, some as young as 2.4 ka, rest unconformably on a Mesozoic greywacke complex. Near-neutral chloride fluids discharge through steeply dipping normal faults in the greywacke into the overlying volcanic units, where they spread laterally through a number of production aquifers. Boiling and dilution are prevalent in both the basement and volcanic units, and these processes significantly affect the chemical characteristics of fluids across the system.more » Production from the volcanic units has met with pressure draw-down and draw-in of cold recharge fluids, whereas production from the basement structures has been largely stable through time. Production induced boiling has resulted in the development of calcite scale in wellbores and, in some extreme cases, in formation rocks.« less
  • The concern about possible decline in Whakarewarewa spring activity led to the creation of the rotorua Monitoring Program and the rotorua Task Force. Both will shortly issue their final reports (Ministry of Energy 1985a,b). Under the Monitoring Program a considerable database was collected about aquifer, well and spring behavior. From this it has been concluded that exploitation has had the following effects: (1) geothermal aquifer pressures have fallen by up to 0.5 bar; geothermal aquifer pressures beneath Whakarewarewa have fallen by about 0.2 bar; and (3) geothermal flow from Whakarewarewa has been reduced by about half. The effects on themore » springs could be reduced by reducing withdrawal particularly near Whaka, reinjection (including the use of downhole heat exchangers), or a combination of these.« less
  • The main object of Comision Federal de Electricidad (CFE`s) Geothermal Field at Los Azufres, is to generate geothermal electricity; however with the new politics in Mexico, CFE has designed a pilot project in order to profit from the geothermal residual energy and to attract national or foreign investors and convince them that direct use of geothermal energy is an attractive feasible and economical project. The object of this paper is to present the CFE experiences in different pilot projects applied to direct uses of geothermal energy.