3D Property Modelling of the Bedrock Hydrostratigraphy in the Fox Creek Area, West-Central Alberta

This report describes the development of 3D model of sandstone abundance we developed to aid hydrogeological conceptualization for the Upper Cretaceous–Paleogene bedrock deposits in the vicinity of Fox Creek, Alberta. The 3D property model of the study area offers new insight into the distribution of aquifers and aquitards within the Upper Cretaceous–Paleogene bedrock deposits.

We derived sandstone abundance from a combination of gamma-ray logs and water well lithological descriptions, and modelled a net sandstone to gross interval thickness (referred to as net-to-gross ratio: NGR). The NGR data were simulated in 3D for a 22 170 km2 area through a series of 10 stacked sub-model domains from the top of the First White Speckled Shale (Wapiabi Formation) to the top of the bedrock surface. This interval includes the Lea Park, Wapiti, Battle, Scollard and Paskapoo formations and is up to about 1800 m in depth. 

The 3D property model illustrates the degree of heterogeneity of sandstone abundance in the bedrock, which can be used to conceptualize the hydrostratigraphy, assuming that the NGR values are a proxy for permeability. Several trends that have hydrogeological implications within the study area emerge as a result of 3D property modelling, including: 
•     a nearly continuous and approximately 230 m thick sandstone unit in the basal portion of the undifferentiated Wapiti Formation; 
•     the absence of a basal sandstone unit within the Paskapoo Formation; 
•     confirmation of abundant but highly heterogeneous sandstone in the uppermost portion of the Paskapoo Formation; 
•     and a general dominance of NGR values of about 0.4 for the Upper Cretaceous–Paleogene bedrock deposits.

The model was created in Schlumberger’s Petrel 2015 and would be appropriate for regional-scale assessments (1:100 000) rather than site-specific investigations.