Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Châteauguay River Basin, a U.S.‐Canada transborder aquifer

Abstract

[1] The Châteauguay River Basin delineates a transborder watershed with roughly half of its surface area located in northern New York State and half in southern Québec Province, Canada. As part of a multidisciplinary study designed to characterize the hydrogeologic properties of this basin, geophysical logs were obtained in 12 wells strategically located to penetrate the four major sedimentary rock formations that constitute the regional aquifers. The layered rocks were classified according to their elastic properties into three primary units: soft sandstone, hard sandstone, and dolostone. Downhole measurements were analyzed to identify fracture patterns associated with each unit and to evaluate their role in controlling groundwater flow. Fracture networks are composed of orthogonal sets of laterally extensive, subhorizontal bedding plane partings and bed-delimited, subvertical joints with spacings that are consistent with rock mechanics principles and stress models. The vertical distribution of transmissive zones is confined to a few select bedding plane fractures, with soft sandstone having the fewest (one per 70-m depth) and hard sandstone the most (five per 70-m depth). Bed-normal permeability is examined using a probabilistic model that considers the lengths of flow paths winding along joints and bedding plane fractures. Soft sandstone has the smallest bed-normal permeability primarily because of its wide, geomechanically undersaturated joint spacing. Results indicate that the three formations have similar values of bulk transmissivity, within roughly an order of magnitude, but that each rock unit has its own unique system of groundwater flow paths that constitute that transmissivity.Citation: Morin, R., R. Godin, M. Nastev, and A. Rouleau (2007), Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Châteauguay River Basin, a U.S.-Canada transborder aquifer,

Structural hydrogeology in the Kenogami uplands, Quebec, Canada /

“…The hydrogeological characterization of a fractured aquifer has been qualified a "challenging task' (Morin et al 2007), as underlined by many examples in this chapter.…”

“…The frequently suggested helpful methodologies for determining hydrogeologic properties of fractured aquifers include: geophysical loggings, geological mapping, rock core descriptions and pumping tests, with particular interest for geophysical logging for identifying trends in the hydrogeological characteristics of the aquifer (Morin et al 2007;Robinson ef al. 2008;Francese et al 2009).…”

“…In geophysical loggings in boreholes, many probes may be used; some of the most recurrent are: fluid temperature and conductance, flowmeter, caliper, acoustic televiewer (ATV), natural gamma, rock resistivity and electrical resistivity (Morin et al 1997(Morin et al , 2007 (see section 4.2.2 for information these probes provide to structural and hydrogeological studies). In the case of fractured aquifers, the ATV is particularly interesting, as it provides information of joint orientation and dip at depth.…”

Numerical Simulation of Groundwater Flow in the Chateauguay River Aquifers

“…Geophysical logs of selected wells indicate that each lithology supports its own flow system and is characterized by a distinct vertical anisotropy (Morin et al, 2007;Nastev et al, 2008). However, drawdown data from large-scale pumping tests yield single permeability type curves typical for porous media, which are analyzed conventionally using the Theis method (Freeze and Cherry, 1979).…”

Application of Geophysical Logging and Straddle Packers for the Investigation of a Fractured Aquifer in a Contaminated Area by Chlorinated Solvents in Sao Paulo State, Brazil

“…The use of these methods began more than 30 years ago [5] [6] and recent studies indicate that they are quite efficient in the study of fractured aquifers [7] [8] [9]. The use of the heatpulse flowmeter helps to define the direction and velocity of vertical component of the water flow in the borehole, which can be used to obtain hydraulic parameters of transmissivity of fractured aquifers [10] [11] [12].…”