HR: 1330h
AN: H32A-0544 [PDF]
TI: Simulating $CO_2$ Leakage and Seepage From Geologic Carbon Sequestration Sites: Implications for
Near-Surface Monitoring
AU: * Oldenburg, C M
EM: cmoldenburg@lbl.gov
AF: Earth Sciences Division, Lawrence Berkeley National Lab
1 Cyclotron Rd., Berkeley, CA 94720 United States
AU: Lewicki, J L
EM: jllewicki@lbl.gov
AF: Earth Sciences Division, Lawrence Berkeley National Lab
1 Cyclotron Rd., Berkeley, CA 94720 United States
AU: Zhang, Y
EM: yqzhang@lbl.gov
AF: Earth Sciences Division, Lawrence Berkeley National Lab
1 Cyclotron Rd., Berkeley, CA 94720 United States
AB:
The injection of $CO_2$ into deep geologic formations for the purpose of carbon sequestration entails risk that $CO_2$ will
leak upward from the target formation and ultimately seep out of the ground surface. We have developed a coupled subsurface
and atmospheric surface layer modeling capability based on TOUGH2 to simulate $CO_2$ leakage and seepage. Simulation results
for representative subsurface and surface layer conditions are used to specify the requirements of potential near-surface
monitoring strategies relevant to both health, safety, and environmental risk assessment as well as sequestration
verification. The coupled model makes use of the standard multicomponent and multiphase framework of TOUGH2 and extends the
model domain to include an atmospheric surface layer. In the atmospheric surface layer, we assume a logarithmic velocity
profile for the time-averaged wind and make use of Pasquill-Gifford and Smagorinski dispersion coefficients to model surface
layer dispersion. Results for the unsaturated zone and surface layer show that the vadose zone pore space can become filled
with pure $CO_2$ even for small leakage fluxes, but that $CO_2$ concentrations above the ground surface are very low due to
the strong effects of dispersion caused by surface winds. Ecological processes such as plant photosynthesis and root
respiration, as well as biodegradation in soils, strongly affect near-surface $CO_2$ concentrations and fluxes. The
challenge for geologic carbon sequestration verification is to discern the leakage and seepage signal from the ecological
signal. Our simulations point to the importance of subsurface monitoring and the need for geochemical (e.g., isotopic)
analyses to distinguish leaking injected fossil $CO_2$ from natural ecological $CO_2$.
This work was supported by the Office of Science, U.S. Department of Energy under contract No. DE-AC03-76SF00098.
DE: 1875 Unsaturated zone
DE: 1899 General or miscellaneous
DE: 3322 Land/atmosphere interactions
SC: Hydrology [H]
MN: 2003 Fall Meeting