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TitreHydraulic conductivity heterogeneity of a local deltaic aquifer system from the kriged 3D distribution of hydrofacies from borehole logs, Valcartier, Canada
AuteurOuellon, T; Lefebvre, R; Marcotte, D; Boutin, A; Blais, V; Parent, M
SourceJournal of Hydrology vol. 351, 2008 p. 71-86,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20080329
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS -72.0000 -71.5000 46.7500 46.0000
Sujetseau souterraine; aquifères; circulation des eaux souterraines; écoulement de la nappe d'eau souterraine; régimes des eaux souterraines; mouvement des eaux souterraines; conductivité; conductivité hydraulique; dépôt deltaïque; hydrogéologie; géomathématique
Illustrationslocation maps; 3-D models; tables; flow charts; plots; histograms
Résumé(disponible en anglais seulement)
The deltaic aquifer system of the Valcartier sector in Quebec, Canada, is part of a quaternary valley fill contaminated by dissolved trichloroethene (TCE). The objective of our study is to define the aquifer system heterogeneity that should influence TCE transport. Heterogeneity is defined by the distribution of both hydrofacies and hydraulic conductivity (K). Hydrofacies are defined as lithologic facies with distinctive hydraulic conductivity ranges. Our approach was developed to take advantage of the abundant stratigraphic and lithologic data provided by borehole logs (7000 m logged from 430 locations). Four site-specific deltaic hydrofacies were defined on the basis of lithologic descriptions, supported by data from grain size analyses, slug tests and cone penetration tests. Each hydrofacies includes a group of geologic facies found in borehole log descriptors to which an initial mean horizontal conductivity KH is associated based on slug tests. Borehole logs were converted to hydrofacies proportions over 5-m intervals to provide 1350 data points. The spatial distribution of hydrofacies was interpolated by three successive interconnected 3D kriging steps using the new technique of "imbricated kriging". Global dual kriging is directly carried out on the 3D grid of a numerical model. Finally, the proportions of hydrofacies were used to estimate horizontal (KH) and vertical (KV) hydraulic conductivity fields using generalized means for layered media. Final KH values assigned to the hydrofacies are calibrated by comparison with 2D trends in KH shown by slug tests. This approach also provides an estimated vertical KV field with a spatially varying proportion to KH, rather than a fixed anisotropy ratio. Imbricated kriging does not preserve the statistical variability of fine scale hydrofacies distribution representative of geological variability. However, the approach provides KH and KV estimates over a 3D numerical grid that are coherent with hydrofacies distribution, which in this case control KH and KV.