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TitleBaseline near-surface bedrock and groundwater geochemical data prior to shale gas development - Preliminary data from southern Quebec
AuthorLavoie, D; Mort, A; Haeri Ardakani, O; Sanei, H; Bordeleau, G; Rivard, C; Aznar, J C
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 154
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130415
PublisherGeological Association of Canada - Mineralogical Association of Canada
MeetingGerological Association of Canada - Mineralogical Association of Canada annual meeting; Fredericton; CA; May 21-23, 2014
Mediapaper; on-line; digital
File formatpdf
NTS21L; 31H; 31I
AreaSt. Lawrence Platform
Lat/Long WENS -75.0000 -71.0000 46.7500 45.0000
Subjectsfossil fuels; geochemistry; hydrogeology; bedrock geology; groundwater geochemistry; groundwater; hydrocarbons; hydrocarbon potential; methane; Uthica Shale; Lorraine Group; Paleozoic; Ordovician
ProgramShale Gas - groundwater, Environmental Geoscience
AbstractIn southern Quebec, from 2006 to 2010, drilling and fracking results have shown that the Upper Ordovician Utica Shale is a potential shale gas producer. In 2010, exploration came to a halt pending an environmental review of all issues related to shale gas exploration and development. The Geological Survey of Canada has initiated a detailed evaluation of shallow and deep sub-surface conditions (geology, hydrogeology, geochemistry, geophysics and geomechanic) at a specific site southwest of Quebec City where one shale gas well targeting the Utica Shale has been drilled and fracked. During the summer and fall of 2013, twenty-five private water wells were sampled and 4 shallow (50 m) wells were drilled, cored and sampled for water chemistry and rock organic geochemistry. In addition, 250 sites were sampled for pore-space radon and hydrocarbons in soils.
The shallow bedrock geology is dominated by Upper Ordovician shales and sandstones of the Lorraine Group, the cap rock of the Utica Shale present at roughly 2 km deep in the subsurface. Rock-Eval and organic matter reflectance results from the organic matter rich Lorraine shales suggest that thermal maturity increases southerly from oil to condensate windows. GC and GC-MS analyses of core extracts document the presence of low but detectable concentrations of C1 to C20 hydrocarbons.
Most water samples have significant concentrations of dissolved hydrocarbons including mostly methane, as well as ethane and propane in a few wells. The presence of dissolved hydrocarbons in groundwater is fairly well established in southern Quebec, although their source (biogenic versus thermogenic) remains ambiguous. The presence of dissolved propane indicates that some of the hydrocarbons are thermogenic in origin. Gas wetness and isotopic ratios (?13C, ?2H) of methane suggest mixed thermogenic and biogenic origin. Areas with elevated radon, methane, ethane and butane in soils are located close of the Appalachians ' St. Lawrence Platform contact, a sector with high concentrations of hydrocarbons dissolved in groundwater.
Summary(Plain Language Summary, not published)
This abstract will present preliminary geochemical data in groundwater, soils and bedrock that were gathered up to now in this project (Environmental Geoscience and Geoscience for New Energy Supply programs). One of the goals of the study is to identify the source of gas present in groundwater in the St. Edouard de Lotbinière (65 km SW of Quebec City). Some preliminary ideas are considered but without certitude so far. This will be explained in the presentation