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Title: Hydrogeochemistry and preliminary reservoir model of the Platanares Geothermal System, Honduras, Central America

Abstract

A detailed hydrogeochemical investigation has been performed at Platanares, Honduras in preparation for shallow geothermal exploration drilling. Platanares is not associated with any Quaternary volcanism but lies in a tectonic zone of late Tertiary to Quaternary extension. Thermal fluids are characterized by pH between 7 and 10, Cl < 40 mg/l, HCO/sub 3/ > SO/sub 4/ > Cl, B less than or equal to 17 mg/l, Li less than or equal to 4 mg/l and As less than or equal to 1.25 mg/l. Various geochemical indicators show that mixing of hot and cold end-member fluids is an important hydrologic process at this site. Geothermometers indicate the geothermal system equilibrated at roughly 225/sup 0/C while trace element chemistry indicates the reservoir resides in Cretaceous red beds of the Valle de Angeles Group. Based on the discharge rates of thermal features, the minimum power output of the Platanares geothermal site is about 45 MW (thermal).

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (USA); Geological Survey, Menlo Park, CA (USA)
OSTI Identifier:
5509256
Report Number(s):
LA-UR-86-1404; CONF-860926-2
ON: DE86010198
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Geothermal Resources Council annual meeting, Palm Springs, CA, USA, 29 Sep 1986; Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GEOTHERMAL FIELDS; GEOCHEMICAL SURVEYS; HONDURAS; GEOLOGIC MODELS; GEOTHERMAL EXPLORATION; CENTRAL AMERICA; DEVELOPING COUNTRIES; EXPLORATION; LATIN AMERICA; SURVEYS; Geothermal Legacy

Citation Formats

Goff, F., Shevenell, L., Janik, C.J., Truesdell, A.H., Grigsby, C.O., and Paredes, R. Hydrogeochemistry and preliminary reservoir model of the Platanares Geothermal System, Honduras, Central America. United States: N. p., 1986. Web.
Goff, F., Shevenell, L., Janik, C.J., Truesdell, A.H., Grigsby, C.O., & Paredes, R. Hydrogeochemistry and preliminary reservoir model of the Platanares Geothermal System, Honduras, Central America. United States.
Goff, F., Shevenell, L., Janik, C.J., Truesdell, A.H., Grigsby, C.O., and Paredes, R. Wed . "Hydrogeochemistry and preliminary reservoir model of the Platanares Geothermal System, Honduras, Central America". United States. doi:. https://www.osti.gov/servlets/purl/5509256.
@article{osti_5509256,
title = {Hydrogeochemistry and preliminary reservoir model of the Platanares Geothermal System, Honduras, Central America},
author = {Goff, F. and Shevenell, L. and Janik, C.J. and Truesdell, A.H. and Grigsby, C.O. and Paredes, R.},
abstractNote = {A detailed hydrogeochemical investigation has been performed at Platanares, Honduras in preparation for shallow geothermal exploration drilling. Platanares is not associated with any Quaternary volcanism but lies in a tectonic zone of late Tertiary to Quaternary extension. Thermal fluids are characterized by pH between 7 and 10, Cl < 40 mg/l, HCO/sub 3/ > SO/sub 4/ > Cl, B less than or equal to 17 mg/l, Li less than or equal to 4 mg/l and As less than or equal to 1.25 mg/l. Various geochemical indicators show that mixing of hot and cold end-member fluids is an important hydrologic process at this site. Geothermometers indicate the geothermal system equilibrated at roughly 225/sup 0/C while trace element chemistry indicates the reservoir resides in Cretaceous red beds of the Valle de Angeles Group. Based on the discharge rates of thermal features, the minimum power output of the Platanares geothermal site is about 45 MW (thermal).},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1986},
month = {Wed Jan 01 00:00:00 EST 1986}
}

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  • This paper is a review and summary of the core drilling operations component of the Honduras Geothermal Resource Development Project at the Platanares geothermal prospect in Honduras, Central America. Three intermediate depth (428 to 679 m) coreholes are the first continuously cored geothermal exploration boreholes in Honduras. These coring operations are part of the Central America Energy Resource Project (CAERP) effort funded by the Agency for International Development (AID) and implemented by the Los Alamos National Laboratory (Los Alamos) in cooperation with the Empresa Nacional de Energia Electrica (ENEE) and the United States Geological Survey (USGS). This report emphasizes coringmore » operations with reference to the stratigraphy, thermal gradient, and flow test data of the boreholes. The primary objectives of this coring effort were (1) to obtain quantitative information on the temperature distribution as a function of depth, (2) to recover fluids associated with the geothermal reservoir, (3) to recover 75% or better core from the subsurface rock units, and (4) to drill into the subsurface rock as deeply as possible in order to get information on potential reservoir rocks, fracture density, permeabilities, and alteration histories of the rock units beneath the site. The three exploration coreholes drilled to depths of 650, 428 and 679 m, respectively, encountered several hot water entries. Coring operations and associated testing began in mid-October 1986 and were completed at the end of June 1987.« less
  • Two slim exploration coreholes to depths of 650 m and 428 m, respectively, have been completed at the Platanares geothermal site, Honduras, Central America. A third corehole is now being drilled. These boreholes have provided information on the stratigraphy, temperature variation with depth, nature and compositions of fluids, fracturing, permeability, and hydrothermal alterations associated with the geothermal reservoir. Eruptions of hot water occurred during the drilling of both the first and third boreholes. Recovery of >98% core has been obtained even under difficult superheated conditions.
  • Our efforts in Honduras and Guatemala were part of the Central America Energy Resource Project (CAERP) funded by the United States Agency for International Development (AID). Exploration core drilling operations at the Platanares, Honduras and Tecuamburro Volcano, Guatemala sites were part of a geothermal assessment for the national utility companies of these countries to locate and evaluate their geothermal resources for electrical power generation. In Honduras, country-wide assessment of all thermal areas determined that Platanares was the site with the greatest geothermal potential. In late 1986 to middle 1987, three slim core holes were drilled at Platanares to a maximummore » depth of 680 m and a maximum temperature of 165{degree}C. The objectives were to obtain information on the geothermal gradient, hydrothermal alterations, fracturing, and possible inflows of hydrothermal fluids. Two holes produced copious amounts of water under artesian conditions and a total of 8 MW(t) of energy. Geothermal investigations in Guatemala focused on the Tecuamburro Volcano geothermal site. The results of surface geological, volcanological, hydrogeochemical, and geophysical studies at Tecuamburro Volcano indicated a substantial shallow heat source. In early 1990 we drilled one core hole, TCB-1, to 808 m depth. The measured bottom hole temperature was 238{degree}C. Although the borehole did not flow, in-situ samples indicate the hole is completed in a vapor-zone above a probable 300{degree}C geothermal reservoir.« less
  • Platanares is located 16 km west of Santa Rosa de Copan, Honduras, along the Quebrada del Agua Caliente. The thermal manifestations are along faults in tuffs, tuffaceous sedimentary rocks, and lavas of the Padre Miguel Group. These tuffs are silicified near the faults, are fractured, and may provide the fracture permeability necessary for the hydrothermal system. Tuffs are overlain by a wedge of terrace gravels up to 60 m thick. Quaternary conglomerates of the Quebrada del Agua Caliente are cemented by silica sinter. The Platanares area contains numerous faults, all of which appear to be extensional. There are four groupsmore » of faults (N80/sup 0/E to N70/sup 0/W, N30/sup 0/ to 60/sup 0/W, N40/sup 0/ to 65/sup 0/E, and N00/sup 0/ to 05/sup 0/W). All hot springs at this site are located along faults that trend mostly northwest and north. Twenty-eight spring groups were described over an area of 0.2 km/sup 2/; half were boiling. Based on surface temperatures and flow rates, between 0.7 and 1.0 MW thermal energy is estimated for the area. The increased temperature of the stream flowing through the thermal area indicates that several megawatts of thermal energy are being added to the stream. We recommend that a dipole-dipole resistivity line be run along the Quebrada del Agua Caliente to identify zones of fracture permeability associated with buried faults and hot water reservoirs within those fault zones. A thermal gradient corehole should be drilled at Platanares to test temperatures, lithologies, and permeability of the hydrothermal system.« less
  • Stratigraphy, temperature profiles, and flow test data from the PLTG-1 and PLTG-2 coreholes in Platanares, Honduras, have been used to determine production characteristics from a 160/sup 0/C fluid zone at 625 to 640 m depth and to estimate depth to the source geothermal reservoir. The two coreholes penetrate thin Quaternary deposits and several hundred meters of Miocene volcanics and Cretaceous to Eocene sedimentary rocks. Extrapolation of the deep thermal gradient of 139/sup 0/C/km in PLTG-2 (depth 401 m) indicates the source reservoir of 220 to 240/sup 0/C fluid occurs at 1.2 to 1.5 km depth. Flow tests of PLTG-1 frommore » the 625 to 640 m zone show that 160/sup 0/C geothermal fluids similar in composition to ''end-member'' hot springs originate from fractured meta-conglomerates of the Valle de Angeles Group. Pressure transient analysis indicates this flow zone taps a localized reservoir having a volume on the order of 0.065 km/sup 3/. Maximum thermal power of PLTG-1 is roughly 3 MW/sub t/. Scaling of aragonite results from flashing of the dilute, high pH, high HCO/sub 3/ fluid. Use of the shallow, 160/sup 0/C resource will require binary cycle power plants and, possibly, downhole pumps to successfully extract heat from the fluids for electrical applications.« less