Hydraulic properties of the Paskapoo Formation in west-central Alberta

Abstract

In an effort to better understand the hydraulic properties of the Paskapoo Formation, hydraulic conductivity and porosity were evaluated for a region in west-central Alberta. Whereas previous studies have focused mainly on sandstone units in the lower portion of the Paskapoo Formation, in southern and central parts of the province, this study focuses on the middle to upper portions. Hydraulic conductivity values were determined by air permeametry for seven drill cores from the area between Hinton and Fox Creek, Alberta. Thin-section petrology and porosity analyses using photomicrographs were also conducted for three of the seven drill cores. Results confirm previous findings that the Paskapoo Formation has heterogeneous hydraulic properties, with horizontal hydraulic conductivity values ranging from 10−10 to 10−5 m/s (determined by air permeametry) and porosity values ranging from 0.02% to 15.3%. The first measurements for the upper sandstone units are provided (1.1 × 10−9 – 2.6 × 10−5 m/s and 0.08%–15.3%) and numerous measurements of the middle siltstone–mudstone unit (1.1 × 10−10 – 4.9 × 10−8 m/s and 0.02%–1.8%) for the northwestern portion of the Paskapoo Formation. Qualitative petrologic analysis suggests that the degree of cementation, rather than grain size, is the dominant control on the hydraulic properties of this portion of the formation. This study determined primary hydraulic properties for both the highly conductive units often considered as aquifers and the low-conductivity units considered as aquitards or confining layers. When combined with previous findings, this study helps expand the understanding of the Paskapoo Formation and provides critical data for assessing groundwater resources.

Application of an Integrated SWAT–MODFLOW Model to Evaluate Potential Impacts of Climate Change and Water Withdrawals on Groundwater–Surface Water Interactions in West-Central Alberta

“…As the Paskapoo Formation is also the shallowest bedrock unit in the area of study, it has exchange between SW and GW [28]. Deposited in the Paleogene, the Paskapoo Formation is a highly heterogeneous fluvial deposit [22] that appears as the shallowest bedrock layer in most of the Little Smoky River watershed. Even within the study area, this formation exhibits a high range in thickness, following a thickening trend toward the foothills [29].…”

“…Even within the study area, this formation exhibits a high range in thickness, following a thickening trend toward the foothills [29]. Three primary units, or members, within the formation have been identified in the study area based on lithological differences, with two aquifers separated by an aquitard [22,30]. The porosity and hydraulic conductivity observed by Hughes et al [22] in these members share a linear relationship, with higher values for both porosity and hydraulic conductivity recorded in the aquifers.…”

“…Three primary units, or members, within the formation have been identified in the study area based on lithological differences, with two aquifers separated by an aquitard [22,30]. The porosity and hydraulic conductivity observed by Hughes et al [22] in these members share a linear relationship, with higher values for both porosity and hydraulic conductivity recorded in the aquifers. In the study completed by Hughes et al [22], average conductivities were 1.3 × 10 −6 m/s and 4.4 × 10 −9 m/s for the sandstone and mudstone/shale units respectively, primarily obtained via air permeameter testing.…”

“…Historically, much of the fresh water required for operations was sourced from the rivers and streams in the region [20], with occasional extraction of GW from freshwater (or near-fresh) aquifers. With increased unconventional Water 2019, 11, 110 3 of 28 resource development comes the potential to use GW to support hydraulic fracturing operations [21,22]. However, a lack of understanding of the total GW and SW availability, reliability and interactions, and limited available projections under future climate change scenarios, may restrict future increases in production of energy resources in the region.…”

“…Many of the formations are both thicker and deeper along the Rocky Mountains but become shallower and are exposed or only covered by a thin layer of sediments to the northeast. Combined with these dipping layers, variability of rock properties within a given geological formation also varies spatially, resulting in a complex hydrogeological environment with widely varying hydraulic conductivity and storage properties [22,24]. These complex but realistic hydrologic and hydrogeologic conditions and the importance of water to support unconventional resource development and sustain rivers, makes it an ideal case study to test the SWAT-MODFLOW model.The primary objective of this study was to apply SWAT-MODFLOW to simulate a large region to study the regional hydrogeological conditions and the potential impacts of climate change and water withdrawal on GW-SW interactions.…”