Vadose Zone and Surficial Monitoring a Controlled Release of Methane in the Borden Aquifer, Ontario.

Abstract:

Development of shale gas resources and potential impacts on groundwater and fugitive gas emissions necessitates further research on subsurface methane gas (CH₄) migration and fate. To address this issue, a controlled release experiment is undertaken at the Borden research aquifer, Ontario, Canada. Due to low solubility, it is expected that the injection will lead to gas exsolution and ebullition. Gas migration is expected to extend to the unsaturated zone and towards the ground surface, and may possibly be affected by CH₄ oxidation. The project consists of multiple components targeting the saturated zone, unsaturated zone, and gas emissions at the ground surface. This presentation will focus on the analysis of surficial CO₂ and CH₄ effluxes and vadose zone gas composition to track the temporal and spatial evolution of fugitive gas. Surface effluxes are measured with flux chambers connected to a laser-based gas analyzer, and subsurface gas samples are being collected via monitoring wells equipped with sensors for oxygen, volumetric water content, electrical conductivity, and temperature to correlate with changes in gas composition. First results indicate rapid migration of CH₄ to the ground surface in the vicinity of the injection locations. We will present preliminary data from this experiment and evaluate the distribution and rate of gas migration. This research specifically assesses environmental risks associated with fugitive gas emissions related to shale gas resource development.