| Titre | Geochemistry of groundwater in the Saint-Édouard area, Quebec, Canada, and its influence on the distribution of methane in shallow aquifers |
| Auteur | Bordeleau, G; Rivard, C; Lavoie, D; Lefebvre, R; Malet, X; Ladeveze, P |
| Source | Applied Geochemistry vol. 89, 2018 p. 92-108, https://doi.org/10.1016/j.apgeochem.2017.11.012 |
| Année | 2018 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20160356 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.apgeochem.2017.11.012 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Québec |
| SNRC | 21L/12 |
| Lat/Long OENS | -71.5000 -71.0000 46.7500 46.5000 |
| Sujets | eau souterraine; méthane; schistes bitumineux; schistes; effets sur l'environnement; contrôles de l'environnement; milieu hydrologique; hydrocarbures; pollution de l'eau souterraine; levés des eaux
souterraines; géochimie des eaux souterraines; puits sales; géologie de l'environnement; géochimie; hydrogéologie |
| Illustrations | location maps; graphs; plots; schematic diagrams |
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| Programme | Gas de schiste - les eaux souterraines, Géosciences de l'environnement |
| Résumé | (disponible en anglais seulement)
Shale gas and tight oil production has undergone a tremendous increase in the last decade in North America, which was accompanied by animated scientific debate
and local public uproar concerning environmental issues, especially the risks of contamination for shallow groundwater resources. In Quebec (eastern Canada), public concerns led to a de facto fracking moratorium in 2010 for the St. Lawrence Lowlands,
where the underlying Utica Shale is known to contain significant gas resources. As only a few exploration gas wells have been drilled, this area may still be considered ¿virgin¿ with respect to exploitation. In 2012, a 4-year project was initiated by
the Geological Survey of Canada, which aimed at characterizing aquifer vulnerability to deep industrial activities in the St-Édouard region, located close to Quebec City in the St Lawrence Lowlands. As part of this project, a baseline study of
hydrocarbons and other geochemical parameters was conducted in shallow aquifers. This paper presents groundwater geochemical characteristics in the region and assesses the geological, hydrogeological and geochemical controls on methane distribution.
Results show that methane is present in 96% of the 48 sampling points over the 500 km2 study area, and that concentrations are highly variable (from 0.006 mg/L to above 80 mg/L), sometimes over short distances and through time. Methane
concentrations appear to be related to specific hydrogeochemical conditions, such as those found below the active groundwater flow zone (0-30 m), where relatively old, chemically evolved water is found under semi-confined to confined conditions. Two
main fault zones are well documented in the area, and there is clear evidence that some deep formation brines, in addition to marine water originating from the Champlain Sea, are migrating into shallow aquifers in the vicinity of the Jacques-Cartier
River fault in the northern part of the study area. This salty groundwater contribution is attributed to the regional groundwater flow coming from the Appalachians and discharging along this normal fault zone close to the St. Lawrence River. The
depth from which the brine originates is, however, unknown, There is no indication that deep thermogenic gas from the Utica Shale is currently reaching the surface, through this pathway or elsewhere in this region. |
| Résumé | (Résumé en langage clair et simple, non publié)
En 2012, une étude multidisciplinaire a été entamée par la Commission géologique du Canada, dans le but d'évaluer la vulnérabilité des ressources
en eau souterraine face à l'exploration ou exploitation éventuelles du gaz de shale, dans la région de St-Édouard, près de Québec, dans les Basses-Terres du St-Laurent. Cet article présente la géochimie naturelle des aquifères peu profonds et la
distribution du méthane dans cette région. Les résultats montrent que le méthane est omniprésent dans la région et que sa présence est principalement liée à des conditions spécifiques des aquifères, telles que de longs temps de résidence de l'eau et
l'absence d'oxygène. Bien qu'on observe la migration de petites quantités de saumures profondes vers les aquifères de surface à proximité et au nord de la faille de Jacques-Cartier, il n'y a aucune indication que du gaz d'origine thermogénique
provenant du Shale d'Utica n'atteit les aquifères en surface par cette zone de faille ou ailleurs dans la région. |
| GEOSCAN ID | 299723 |
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