HR: 1340h
AN: B33A-1006    [Abstracts]
TI: Application of Soil Gas Composition, Carbon Isotopes, and Gas Fluxes to the Atmosphere in Order to Detect Low Rates of Leakage from CO₂ Sequestration Projects
AU: * Klusman, R W
EM: rklusman@mines.edu
AF: Colorado School of Mines, Dept. of Chemistry and Geochemistry, Golden, CO 80401 United States
AB: Carbon dioxide sequestration in spent oil and gas fields will likely be a significant early option that has economic advantages. A concern is the potential for gas microseepage under the overpressured conditions necessary for operation, particularly for indigenous CH₄. A comparison was made between the overpressured Rangely, Colorado CO₂ operation and the underpressured Teapot Dome oil field in Wyoming. Fluxes of CO₂ into the atmosphere under winter conditions of low soil biological activity were similar, whereas fluxes of CH₄ were different by a factor of 100, respectively, for Rangely and Teapot Dome. Shallow soil gas composition was similar for CO₂, but also exhibited large differences for CH₄, reflecting high rates of microseepage at a few locations related to faulting. Near-surface CH₄ will be potential trouble in oil and gas field sequestration operations. Stable carbon isotope and carbon-14 measurements aided in the recognition of anomalous areas, and in identifying gas sources. Ten-meter deep holes were augured for nested soil gas sampling at selected locations of interest for more thorough characterization. In anomalous locations, a substantial proportion of deep-sourced CH₄ was microbially oxidized in the unsaturated zone, producing isotopically distinctive and radiocarbon-depleted CO₂. Carbon isotopic composition of surface materials, such as calcite, caliche, vegetation, soil organic and inorganic matter are essential in the characterization of processes operating in the near-surface.
DE: 0428 Carbon cycling (4806)
DE: 0452 Instruments and techniques
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005