Modeling Multiscale Heterogeneity and Aquifer Interconnectivity

A number of methods involving indicator geostatistics were combined in a methodology for characterizing and modeling multiscale heterogeneity. The methodology circumvents sources of bias common in data from borehole logs. We applied this methodology to the complex heterogeneity within a regional system of buried valley aquifers, which occurs in the western glaciated plains of North America and includes the Spiritwood Aquifer. The region is conceptualized as having a hierarchical organization with three facies assemblage types (large‐scale heterogeneity) and two facies types within each assemblage (small‐scale heterogeneity). We statistically characterized the sedimentary architecture at both scales, formulated indicator correlation models from those characterizations, and used the models to simulate the architecture in a multiscale realization. We focused on the interconnectivity of units creating higher‐permeability pathways. Higher‐permeability pathways span the realization even though the proportion of higher‐permeability facies is less than the percolation threshold. Thus, geologic structures as represented in the indicator correlation models create interconnectivity above that which would occur if the higher‐permeability facies were randomly placed. This amount of interconnection among higher‐permeability facies within the multiscale realization is consistent with that suggested in prior hydraulic and geochemical studies of the regional system.