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TitleA study of potential links between the Utica Shale and shallow aquifers in St-Édouard, southern Quebec, Canada
AuthorRivard, CORCID logo; Bordeleau, G; Lavoie, DORCID logo; Ladevèze, P; Duchesne, M; Pinet, N; Ahad, JORCID logo; Lefebvre, R; Aznar, J C; Pugin, A; Crow, HORCID logo; Séjourné, S; Labrie, D
SourceAIH-CNC Waterloo 2015; 2015 p. 1
Alt SeriesEarth Sciences Sector, Contribution Series 20140456
MeetingAIH-CNC Waterloo 2015 - 2015 Canadian Hydrogeology Conference - International Association of Hydrogeologists Canadian National Chapter; Waterloo, ON; CA; October 27-30, 2015
File formatdoc
Lat/Long WENS -72.0000 -71.5000 46.7500 46.5000
Subjectsfossil fuels; hydrogeology; environmental geology; geophysics; geochemistry; engineering geology; Nature and Environment; Science and Technology; Economics and Industry; Government and Politics; petroleum resources; petroleum industry; hydrocarbons; gas; hydrocarbon recovery; groundwater resources; groundwater geochemistry; groundwater pollution; aquifers; bedrock geology; lithology; sedimentary rocks; shales; sandstones; structural features; fractures; faults; hydraulic fracturing; fluid migration; hydraulic analyses; permeability; hydraulic conductivity; geophysical surveys; seismic surveys; e m surveys, airborne; magnetic surveys, airborne; aeromagnetic surveys; acoustic surveys; geophysical logging; boreholes; core samples; observation wells; gas wells; stable isotope studies; soil geochemistry; ethane; propane; methane; thermal analyses; salinity; Utica Shale; alkanes; natural sources; anthropogenic sources; regulation; water management
ProgramEnvironmental Geoscience, Shale Gas - groundwater
Released2015 10 01
AbstractPotential links between a deep gas shale formation and shallow aquifers are being investigated in southern Quebec (Canada), near a shale gas well drilled and fracked in 2009-2010. A large set of data has been collected to detect potential natural fluid migration pathways. Acquired data include hydrogeological, geophysical, geochemical, as well as geomechanical data. Hydrogeological work involved drilling, permeability tests and structural surveys of outcrops. Geophysical surveys comprised shallow high-resolution seismic, borehole logging in the newly drilled shallow wells, as well as airborne Transient-Electro-Magnetic and magnetic surveys. Groundwater from 44 wells was sampled and analyzed for a wide range of compounds, and 6 of these wells were chosen for continued monitoring of dissolved alkane concentration and isotopes (every 3 months). Soil and core samples were also collected to determine their hydrocarbon content. Geomechanical properties of deep shale formations were studied using both acoustic geophysical logs and core samples.
Geochemical data show that methane is present throughout the study area, but in highly variable concentrations (from nearly 0 to 40 mg/L), while ethane and propane are only found in a few wells. Preliminary results indicate that alkane concentrations are strongly correlated to the water type, well depth and groundwater age. They also show that all samples would contain bacteriogenic methane, and from 20 to 40% would also have a thermogenic component. Additional analyses on groundwater and core samples are ongoing to better identify the methane source. The geophysical interpretation, including deep and shallow data, suggests that possible pathways could be present. However, hydraulic tests have not indicated different permeabilities close to known faults. Permeabilities in the shallow and naturally fractured shale rock aquifers vary from moderate where sandstone beds occur (1 000 000 - 10 000 000 m/s) to low when mostly black shale is present (1 000 000 000 - 100 000 000 m/s). Borehole logging showed that most of the permeable fractures occur in the upper 40 m and that permeability usually rapidly decreases with depth. Brackish water in one well was encountered at about 140 m deep, confirming that active groundwater flow is very shallow. Geomechanical data further indicate that the caprock geological units above the gas shale act as a good protection against potential contamination from deep fluids. This study integrates data from multiple sources in order to acquire the necessary knowledge to support provincial regulations and water management to insure that aquifers would not be adversely affected by shale gas development, at least from a geological point of view.
Summary(Plain Language Summary, not published)
Results (nearly final) of our St-Edouard project on potential impacts of shale gas development on aquifers will be presented at this conference (October 2015). Results of the 2014 summer and fall field campaign will be combined to those of the 2013 campaign. The origin of methane will have been identified, mainly based on geochemical data. It looks like we will be able to say that the caprock in this region forms an efficient protection unit, based on geomechanical and hydrogeological data.

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