Assessment of Potential Impacts of Shale Gas Development on Shallow Aquifers in the St. Lawrence Lowlands, Quebec, Canada
French Title: Évaluation des Impacts Potentiels du Développement Lié au Gaz de Schiste sur les Aquifères de Surface dans les Basses-Terres du St-Laurent, Québec, Canada
Previously Published Material: Preliminary data have been presented in other conferences.
English Abstract:
The Upper Ordovician Utica Shale in the St. Lawrence Lowlands has a shale gas production potential, which was assessed by the industry between 2007 and 2010, until a
de facto moratorium was imposed on shale gas exploration in Quebec. A total of 29 wells were drilled in this shale, of which 18 were subjected to hydraulic fracturing. Due to this limited number of wells, the Utica Shale is considered a frontier play and, therefore, the St. Lawrence Lowlands are viewed as a “virgin” area with regards to fracking. The Geological Survey of Canada initiated a project in 2012 in the St-Edouard area, 65 km south-west of Quebec City, to investigate whether this region is geologically at risk before drilling and fracking activities resume. This area was selected because the Talisman St-Édouard well is the most promising one drilled in the Utica Shale and it is also located in a region where several faults are present. Multi- source data are being used for this study and extensive fieldwork has been carried out, including sampling of groundwater, soil, core and drill cuttings, shallow seismic surveys (~800 m), borehole geophysics in shallow wells (30 to 150 m deep) and hydraulic tests in sediments and bedrock. Furthermore, geomechanical lab tests and chemical lab analyses, as well as interpretation of acoustic logs and deep seismic profiles are being done.
The anticipated outcomes of this work are two-fold. First, this work will provide a better understanding of potential impacts of shale gas development on shallow aquifers through the identification of possible natural connections between deep and shallow geologic formations. Second, the development of a methodology for the estimation of aquifer vulnerability relative to activities occurring at depth will be initiated based on this work. This methodology could serve as a basis for permit allocation and regulations to insure that needed studies are being conducted by the industry along with exploration activities.
