Fate of Fugitive Natural Gas in Heterogeneous Near‐Surface Sediments in a Region of Extensive Petroleum Resource Development
Jessie Tse‐Hua Chao, Aaron G. Cahill, Cole J.C. Van De Ven, Roger Beckie
Abstract
Abstract Fugitive natural gas released in the subsurface from leaking oil and gas wells can affect groundwater quality and generate significant greenhouse gas emissions to the atmosphere. We released natural gas into a Western Canada Sedimentary Basin (WCSB) groundwater system located in an area of petroleum resource development. Through 55 depth‐discrete monitoring points installed up to 26 m deep, we tracked spatiotemporal evolution of dissolved gases over 760 days. Fugitive gas was diverted and mostly retained in the subsurface by capillary barriers, resulting in highly irregular distribution and dissolution of multicomponent gas constituents. Gas wetness changed significantly during migration, although stable‐carbon isotope ratios did not. We expect that where a surface diamict is present, typical of the WCSB, a significant portion of fugitive gas released from leaky wells will be retained in the subsurface, mitigating greenhouse gas emissions to the atmosphere but inferring greater risk on groundwater.