Surface CO2 leakage during two shallow subsurface CO2 releases

• Published in: Geophysical research letters Vol. 34; no. 24; pp. L24402 - n/a
• Main Authors: Lewicki, J. L., Oldenburg, C. M., Dobeck, L., Spangler, L.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01-12-2007; Blackwell Publishing Ltd
• Subjects: Biogeosciences; carbon dioxide; Diel, seasonal, and annual cycles; Earth sciences; Earth, ocean, space; Exact sciences and technology; geologic carbon sequestration; Hydrology; Instruments and techniques; leakage; Modeling; Trace gases; carbon dioxide; geologic carbon sequestration; leakage; models; physical properties; detection; dissolution; ground water; water table; respiration; storage; subsurface; Modeling; depth; aquifers; discharge; migration; prediction; soils
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2007GL032047

A new field facility was used to study CO2 migration processes and test techniques to detect and quantify potential CO2 leakage from geologic storage sites. For 10 days starting 9 July 2007, and for seven days starting 3 August 2007, 0.1 and 0.3 t CO2 d−1, respectively, were released from a ∼100‐m long, sub‐water table (∼2.5‐m depth) horizontal well. The spatio‐temporal evolution of leakage was mapped through repeated grid measurements of soil CO2 flux (FCO2). The surface leakage onset, approach to steady state, and post‐release decline matched model predictions closely. Modeling suggested that minimal CO2 was taken up by groundwater through dissolution, and CO2 spread out on top of the water table. FCO2 spatial patterns were related to well design and soil physical properties. Estimates of total CO2 discharge along with soil respiration and leakage discharge highlight the influence of background CO2 flux variations on detection of CO2 leakage signals.