THE PRESENCE OF THE MIDDLE RUN FORMATION ACROSS SOUTH-CENTRAL INDIANA CONFIRMED BY NEW 2D SEISMIC ACQUISITION

The Middle Run Formation, which lies below the Mount Simon Sandstone (Upper Cambrian), has been mapped and identified in deep wells and sparse seismic data across Ohio and Indiana. The Middle Run formation was discovered and named after the drilling of a deep test well and seismic line in Warren County Ohio by the Ohio Department of Natural Resources between 1987 and 1989 (Shrake et al. 1990, Shrake, 1991). Deep well penetrations and data are sparse, as many wells in the region target hydrocarbons in the shallower Trenton or Knox formations. New data including 2D seismic and upcoming deep well tests as part of this study advance the knowledge of the Middle Run characteristics in southern Indiana.

New 2D seismic data were acquired in 2024 in in south-central Indiana. The seismic lines image a unit between the base of the Mount Simon and a strong high impedance reflector, assumed to be crystalline basement. Observations include an overall westward dipping package (< 0.5 deg) of sediments infilling the rugose Precambrian basement topography. The top of the Middle Run Formation deepens from approximately -4400 ft TVDSS to -6600 ft TVDSS from east to west across southern Indiana with thicknesses ranging from 800-2300 ft over basement topography. These sediments do not show large scale faulting or deformation from Precambrian structures. Overall westward thickening suggests a sediment source from the east and may be associated with Grenville provenance. These observations differ from the Middle Run geometry, thickness and dip as documented in western Ohio (Shrake, 1991) but support Precambrian clastic assemblages documented by Pratt et al. 1992 across the midcontinental US. Results from upcoming deep well tests will confirm the presence and well log characterization of the upper portion of the Middle Run and aid in future studies.