Stochastic Modeling of the Paskapoo Formation

Current groundwater resource practice for the evaluation of non-ideal groundwater systems is unable to address the heterogeneity inherent in these systems. In Alberta, the Farvolden Q20 method is used for evaluating long-term water well yield from an aquifer. This concept is based on the theoretical estimate of water level drawdown in a pumping well after 20 years of pumping. The concept offers an estimation of maximum well yield but is based on a simplistic aquifer model which under many circumstances may result in faulty estimates in long-term yield (SRC 2006). Since 1959 there have been advances in pressure transient analysis that can be utilized to improve the evaluation of long-term yield.;In Alberta, the Paskapoo Formation covers 10,000 km2 and is located adjacent to the deformed belt east of the Foothills. It is the largest single source of groundwater in the Canadian Prairies with approximately 85% of the wells being located between the cities of Calgary and Red Deer.;The continental sediments of the Paskapoo Formation represent the late-stage foreland infill (Hamblin 2004). The Paskapoo formation is located in the north central and south central regions of Alberta and formed within a high energy sedimentation environment that attained a maximum thickness of 900 m within the core of the Alberta Syncline (Jerzykiewicz 1997, Hamblin, 2004).;The Paskapoo is geologically complex and is comprised of the Haynes member, Lacombe member, and the Dalehurst member. The Haynes member consists of thick, massive, and coarse-grained sandstones. The Lacombe member overlies the Haynes members and consists of channel sand and complexes encased in floodplain deposits which are characterized by siltstone, mudstone, shale, and minor coal. The Dalehurst member overlies the Lacombe member and is only present near the Hinton area immediately adjacent to the Foothills and is an erosional remnant.;The Paskapoo Formation is part of the Scollard-Paskapoo aquifer which lies at the top of the Cretaceous-Tertiary succession in the Alberta Basin. The hydrogeology of the system is very complex. The stratigraphy consists of randomly arranged sand channels and complexes embedded in low permeability overbank/flood plain deposits. Spatial distribution and connectivity of the permeable facies is variable and as such water yield is highly variable. Regionally, the system is topographically driven and pressures are slightly subhydrostatic (Bachu et al 2003).;The Scollard-Paskapoo system consists of a groundwater flow toward the north-northeast in a shallow gravity driven aquifer system characterized by meteoric recharge along local and regional topographic highs (Harrison et al 2006, Vogwill 1983). The elevation versus pressure head data indicate a moderately positive correlation suggesting that there is a regional topographic effect on flow (Harrison et al 2006).;High yielding areas of the Paskapoo Formation with fracturing have been classified as moderate to poor aquifers with yields range from less than 9 m3/d to 35 m3 /d (Vogwill 1983). Yields in other areas have been recorded as high as 3200 m3/d in the Wabamun Lake region (Harrison et al 2006). Transmissivity for Paskapoo aquifers ranges from less than 1.5 m2/d to over 100 m2/d, but has been recorded as high as 1,000 m2/d. Storativity values range from 5 x 10-5 to 10-4. Regional permeability data for the Paskapoo indicate values ranging from 10 to 1000 millidarcies where the fracture network is present (Vogwill 1983).;The geology of the Paskapoo represents a heterogeneous anisotropic system consisting of a non-marine succession of irregular sandstone channels of variable thickness and sinuosity embedded in overbank deposits with a 3-dimensional fracture overprint. The level of geologic complexity and uncertainty present within the Paskapoo Formation calls for the implementation of alternative workflows and methods for the evaluation of subsurface data.;A stochastic 3-dimensional geomodel approach to run a series of simulations that contain hydrofacies with geologically realistic shapes to produce realistic sharp physical and hydrologic boundaries between hydrofacies representative of the Paskapoo Formation for subsequent upscaling and simulation of steady-state and transient conditions is proposed in this project. A geomodel is developed using statistically relevant data based on an analogue model developed by Burns et al. (2010b). Property modeling is completed during the geomodeling process whereby the grid cells are populated with statistically appropriate geologic and hydraulic values. A series of simulated transient pumping tests are performed to evaluate system response and the utility of both long-term (approximately 8 to 15 hours) and short-term tests (4 hours) and subsequently the application of the Farvolden Q20.;Pressure transient analysis is used to evaluate the transient pressure data to identify the presence of boundaries, prevailing flow regimes, and for parameter estimation. (Abstract shortened by UMI.)...