10 YEARS OF RESEARCH ON POTENTIAL IMPACTS OF UNCONVENTIONAL HYDROCARBON EXPLOITATION ON GROUNDWATER QUALITY: LOOKING BACK AND FORWARD

Since the 2010’s, unconventional oil and gas (O&G) production has raised concerns regarding the potential contamination of shallow aquifers through upward migration of natural gas and other contaminants. Among the many groups having conducted research on this topic, the Geological Survey of Canada has launched three major multidisciplinary projects in study areas of similar sizes (500-700 km²), but with very different geological and O&G development contexts. The first project took place in Saint-Edouard (Québec), where no commercial O&G production has occurred. The second project was in a region of moderate hydrocarbon production (southern New Brunswick; 39 O&G wells). The third project is located in a region that has experienced significant production over the past 50 years (Fox Creek, Alberta; >775 O&G wells). A thorough methodology has been developed to identify the origin of methane in shallow groundwater of these regions.

Interestingly, the complexity in identifying the origin of methane, and hence assessing the occurrence of contamination, was not found to be related to the number of O&G wells in a region, but rather to the geological and hydrogeological characteristics of this region. Some areas exhibit naturally high concentrations of methane, which has sometimes been affected by various processes, making source identification more challenging. In all three regions, no anthropogenic contamination has been identified. Methane was indeed shown to be naturally occurring, even when its isotopic composition resembled that of thermogenic gas.

However, this might change in the future, as the estimated 370 000 abandoned O&G wells in Canada (in addition to the currently active wells) continue to age, and their structural integrity may eventually be compromised. Considering this, the methodology developed to identify the origin of hydrocarbons in groundwater is likely to be very useful in identifying leaks, provided that adequate groundwater monitoring is conducted near abandoned O&G wells. Furthermore, many other energy-related activities involving deep geological units (e.g., CO₂ sequestration, hydrogen storage) are expected in the near future. We should therefore build on the lessons learned from 10+ years of O&G environmental impact research to develop guidelines for these new “green” activities.