MAPPING PERMEABILITY IN THE ST FRANCOIS AQUIFER, MISSOURI

Although the St. Francois aquifer is a prolific source of groundwater in southeastern Missouri, it is utilized very little throughout the rest of the state due to the presence of the shallower Ozark aquifer. Nevertheless, the St. Francois aquifer is useful as both a supplementary groundwater source for those experiencing Ozark aquifer depletion and a CO₂injection target in the saline northern portion of the aquifer.

The Lamotte Sandstone is the primary water-bearing unit of the St. Francois aquifer, as well as the basal Cambrian unit in Missouri. The Reagan Sandstone lies above the Lamotte, separated by low-permeability formations, and is present in parts of southwest Missouri. We measured the transmissivity and hydraulic conductivity of these sandstones via single-well pumping tests at three Missouri Carbon Sequestration Program sites and analyzed time-drawdown and specific-capacity measurements from additional historical sites from the Missouri Geological Survey.

Transmissivity and hydraulic conductivity (K) are functions of the aquifer's permeability; these vary inversely with depth. Depths greater than ~370m below ground surface are seen to have decreased K due to pervasive cementation. Using the derived permeability data for these functions, maps have been made to delineate areas with higher likelihood for successful high-capacity wells.

This material is based on work sponsored by the Department of Energy National Energy Technology Laboratory under Award Number DE-NT0006642 to City Utilities of Springfield, MO