Model for Characterizing a Shallow Bedrock Aquifer in Central Lower Michigan- Heterogeneity and Discontinuity Dominates the System

Niah B. H. Venable, Geosciences Department, Western Michigan University, Kalamazoo, MI, [email protected]

Past studies of the Pennsylvanian Saginaw Aquifer suggested an incised valley fill relationship between the Grand River and Saginaw Formations comprising the aquifer.  Recent findings supported by core analysis, wireline log correlation and biostratigraphic work replace previous models.  This model suggests a regression period dominated by deltaic deposition changing upsection to meandering stream complexes capped by transgressive estuarine conditions.   

These findings have important implications for aquifer heterogeneity both vertically and horizontally.  Although, some coarse-grained channel sand units are as thick as 20-25 meters, lateral discontinuity of reservoir quality material is at a scale smaller than well spacing.  

Water well data from a State of Michigan Geographic Information Systems database incorporated into this study supplies a proxy for core material where needed and water production data.  This dataset pairs with oil and gas wells across the study area to allow hydrologic interpretations regarding the aquifer units.   

Ongoing work will utilize the new regressive-transgressive model to delineate the spatial and geometric distributions of reservoir-quality aquifer units in this area.  This is important due to increasing water consumption pressures from municipal and industrial sources in the region.