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Title: Numerical modeling of cold magmatic CO2 flux measurements for the exploration of hidden geothermal systems

Journal Article · · Journal of Geophysical Research. Solid Earth
DOI:https://doi.org/10.1002/2015JB012258· OSTI ID:1501370
 [1];  [2];  [3]
  1. Universidad Nacional Autónoma de México, Temixco (Mexico)
  2. Univ. of Bern (Switzerland)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
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The most accepted conceptual model to explain surface degassing of cold magmatic CO2 in volcanic-geothermal systems involves the presence of a gas reservoir. Here, numerical simulations using the TOUGH2-ECO2N V2.0 package are performed to get quantitative insights into how cold CO2 soil flux measurements are related to reservoir and fluid properties. While the modeling is based on flux data measured at a specific geothermal site, the Acoculco caldera (Mexico), some general insights have been gained. Both the CO2 fluxes at the surface and the depth at which CO2 exsolves are highly sensitive to the dissolved CO2 content of the deep fluid. If CO2 mainly exsolves above the reservoir within a fracture zone, the surface CO2 fluxes are not sensitive to the reservoir size but depend on the CO2 dissolved content and the rock permeability. For gas exsolution below the top of the reservoir, surface CO2 fluxes also depend on the gas saturation of the deep fluid as well as the reservoir size. The absence of thermal anomalies at the surface is mainly a consequence of the low enthalpy of CO2. The heat carried by CO2 is efficiently cooled down by heat conduction and to a certain extent by isoenthalpic volume expansion depending on the temperature gradient. Thermal anomalies occur at higher CO2 fluxes (>37,000 g m-2 d-1) when the heat flux of the rising CO2 is not balanced anymore. Lastly, specific results are obtained for the Acoculco area (reservoir depth, CO2 dissolved content, and gas saturation state).

Research Organization:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Fossil Energy (FE); Swiss Competence Center for Energy Research‐Supply of Energy (SCCER‐SOE); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Geothermal Technologies Office
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1501370
Journal Information:
Journal of Geophysical Research. Solid Earth, Vol. 120, Issue 10; ISSN 2169-9313
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 8 works
Citation information provided by
Web of Science

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Related Subjects

58 GEOSCIENCES
TOUGH2
numerical modeling
CO2 degassing
Acoculco
geothermal
exploration