Aligning Groundwater Mapping with the Scale of Regulation in the Fox Creek Area

Developing the liquid-rich shale gas plays of the Duvernay and Montney formations in west-central Alberta relies on non-saline water for hydraulic fracturing, which currently is often sourced from surface water and shallow groundwater in the Fox Creek area. To regulate these developments, the Alberta Energy Regulator (AER) and Alberta Environment and Parks (EP) have indicated that there is a need for quantifying and managing cumulative effects of water use at a regional scale. Such a regional scale approach requires scientifically defensible geoscience at a scale that is comparable to both the development and regulation.

As part of evaluating Alberta’s groundwater inventory, the Alberta Geological Survey (AGS) is nearing completion of a hydrogeological characterization project focused on a 22 000 km2 area centred on Fox Creek. This project aims to advance the understanding of regional groundwater resources by: (i) producing a 3D hydrostratigraphic model of the Quaternary, Neogene, and Upper Cretaceous formations (i.e. Lea Park Fm. up to ground surface); (ii) quantifying rates of recharge, discharge, and interaction with surface water; and (iii) developing a conceptual model for non-saline groundwater circulation.

To support hydrostratigraphic modelling for this large area, a variety of data sources are being used, including: gamma-ray geophysical logs made through surface casing; legacy borehole logs from Alberta Research Council coal mapping, project-specific field mapping program that was completed in 2015, and lithological descriptions from the Alberta Water Well Information Database. Together, these data have been used to significantly revise the bedrock topography of the area and partition geological formations into a series of slices to evaluate major sandstone trends (i.e. net-to-gross sandstone ratio). Preliminary findings reveal that the depth to bedrock is shallower than previously shown and that many of the extensive bedrock plateaus are gravel-capped, which will influence patterns of groundwater circulation in the region.

Compared to hydrostratigraphic modelling, hydrogeological characterization has focused on the uppermost bedrock unit, which is predominantly the Paskapoo Formation. Groundwater mapping has relied on the Alberta Water Well Information Database and two multi-level piezometers installed adjacent to the Little Smoky River as part of this project. Preliminary findings show that the prevailing groundwater flow direction appears to be downward in the Paskapoo Formation (i.e., recharge condition), except for localized flow systems that provide base flow to rivers in the study area (e.g., Simonette River, Little Smoky River). Sampling of environmental tracers (stable isotopes of water, tritium, noble gases) from four rivers in the area is helping better define groundwater interaction with rivers and interpret groundwater residence times.

The objectives and approach of this project have been designed to meet the anticipated needs of regulators and industry, at a scale suitable for cumulative effects management initiatives. The resultant conceptualization will encompass the geologic framework and hydrodynamics, and become the basis for subsequent development of coupled groundwater-surface water numerical models within the Fox Creek region.