Three-Dimensional Characterization of a Fluvial Sandstone Reservoir Analog in Northeast Kansas Using High-Resolution Ground-Penetrating Radar

Alex Martinez, Howard R. Feldman, Joseph M. Kruger, and D. Scott Beaty

Small-scale lateral variations in sandstone permeability and porosity can have dramatic implications for oil and gas field development and productivity. Unfortunately, these variations occur at scales much smaller than typical well spacing, such that one must turn to outcrop analogs in order to predict the architecture of the small-scale stratigraphic complexities. Ground-penetrating radar (GPR) data were processed using conventional seismic software and interpreted on a workstation to map 3-D geometries of bounding surfaces in fluvial sandstone facies of the Upper Pennsylvanian Tonganoxie sandstone. This sandstone is productive in at least one location and is thought to be an analog for some Upper Morrow incised valley fill sandstone reservoirs. High-frequency (500 MHz) PR data were used to obtain decimeter-scale resolution from the surface to a maximum depth of 5 m. The primary study data are a grid of 2-D profiles spaced 1.52 m apart over a 30.5 × 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. Outcrop photomosaics reveal that tabular planar cross bed 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 in either the paleoflow direction or normal to it. At least one sandstone body is greater than 30.5 m lon . Future work involves integrating minipermeameter and gamma-ray data in order to correlate GPR reflections with permeability variation.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California