Results of investigation at the Miravalles geothermal field, Costa Rica. Resultados de las investigaciones en el campo geotermico de Miravalles, Costa Rica; Parte 2, Muestreo de fluidos pozo abajo

Technical Report · Sun Oct 01 00:00:00 EDT 1989

DOI:https://doi.org/10.2172/5531696· OSTI ID:5531696

Grigsby, C O; Goff, F; Trujillo, Jr, P E; Counce, D A; Dennis, B; Kolar, J; Corrales, R ^[1]

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1. Los Alamos National Lab., NM (USA)

Samples of the geothermal fluids in the Miravalles, Costa Rica, geothermal system were collected from production wellbores using downhole fluid samplers, from flowing wellheads using miniseparators, and from hot springs that discharge in the area. The reservoir fluid at Miravalles is a neutral-chloride-type water, but fumaroles and acid-sulfate springs are present within the main thermal area, and there are bicarbonate-rich hot springs that are clearly related to the neutral-chloride reservoir fluids. Dissolved gases are primarily a mixture of CO{sub 2} with air, but samples collected in the fumarolic areas also contain H{sub 2}S. Water-stable isotope analyses suggest local meteoric recharge, and the reservoir fluid shows oxygen isotopic shifts of about 2.5% due to high-temperature oxygen exchange between water and rock. Chemical geothermometer temperatures are consistent with the measured downhole temperature of 220{degrees} to 255{degrees}C. This pattern of neutral-chloride reservoir fluids with acid-sulfate springs near the source region and bicarbonate-rich chloride hot springs at the periphery of the system suggests a lateral outflow type of hydrothermal system. In addition to the geochemical evidence, temperature profiles from several of the wells show temperature reversals that are characteristic of lateral outflow plumes. We find no evidence for the underlying, higher temperature (300{degrees}C) system, which has been suggested by other investigators. 24 refs., 14 figs., 6 tabs.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: AID
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5531696
• Report Number(s): LA-11510-MS-Pt.2; ON: DE90001891
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
GEOTHERMAL FLUIDS
GEOCHEMICAL SURVEYS
CHLORIDES
COSTA RICA
GEOTHERMAL WELLS
HYDROGEN SULFIDES
SULFATES
CENTRAL AMERICA
CHALCOGENIDES
CHLORINE COMPOUNDS
DEVELOPING COUNTRIES
FLUIDS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
LATIN AMERICA
OXYGEN COMPOUNDS
SULFIDES
SULFUR COMPOUNDS
SURVEYS
WELLS
Geothermal Legacy
150303* - Geothermal Exploration & Exploration Technology- Exploratory Drilling & Well Logging