This paper is an adaptation of a poster presented at the 1996 annual AAPG meeting in San Diego.
The Tonganoxie Sandstone (Upper Pennsylvanian) is thought to be an analog for some Upper Morrow incised valley-fill sandstone reservoirs, and it is productive in at least one location. High-frequency (500 MHz) ground-penetrating radar (GPR) data were used to obtain decimeter-scale resolution from the surface to a maximum depth of 5 m at a study site over the Tonganoxie Sandstone in northeast Kansas. The primary study; data are a grid of 2D profiles spaced 1.5 m apart over a 30.5 m x 30.5 m area. Both individual foresets and bedset bounding surfaces were successfully imaged. Bounding surfaces are potential zones of reduced permeability and may result in reservoir compartmentalization. GPR data were processed using conventional seismic software and interpreted on a workstation to map 3D geometries of bounding surfaces.
Outcrop photomosiacs reveal that tabular planar crossbed sets generally thin upwards from 1.0 m thick at the base of the outcrop to 0.3 m thick near the top, probably reflecting an individual channel fill. GPR results reveal that shapes of sandstone bodies are highly variable, with their long axis either parallel to paleoflow direction or normal to it. At least one sandstone bedset is greater than 30.5 m long. Integration of minipermeameter and GPR data reveal that surfaces of low permeability can be mapped through GPR methods.