Geochemical compositions of subsurface materials and the potential impacts on groundwater quality from fugitive methane within the Peace Region, British Columbia

Methane accumulation in groundwater from gas migration induced by hydrocarbon extraction can lead to degradation of water quality. This research focuses on the potential impact elevated concentrations of methane can have on shallow groundwater systems based on the geochemical properties of the sediments and rocks that are present. Bulk chemical characterization of major oxides, trace elements, and rare earth elements indicate that lithologically similar geologic materials in the Peace Region of British Columbia share some geochemical similarities at a regional scale. Investigation of hydrogeochemical characteristics through sequential extraction experiments suggests there is little difference between materials regarding their potential for mobilization of trace elements into groundwater. PHREEQCi numerical models of methane interacting with these materials indicate there is a greater impact in reducing compared to oxidizing conditions, and the presence of carbonate and iron oxyhydroxide minerals mediate the influence large fluxes of methane have on the hydrochemistry.