The KU ERC provided seed funds to help in the initial equipment purchases related to ground-penetrating radar (GRP). These and matching funds from other KU departments have grown this project into a significant, and cutting-edge program on campus. A summary is provided in the following three paragraphs exerted from a recent paper on this new GPR technology (Martinez, Kruger, and Franseen, 1998). In addition, references are cited below that have utilized this equipment.
Summary of GPR Technology from Martinez, Kruger, and Franseen (1998)
Ground-penetrating radar (GPR) is a near-surface, non-intrusive geophysical technique similar to seismic reflection that images the subsurface at a much higher resolution. In addition to the high-resolution imaging, GPR is a potentially useful method in outcrop studies because it can provide stratal information in poorly exposed areas and three-dimensional stratal characteristics beyond the outcrop face. Because GPR profiles are usually gathered as common offset data, minimal digital-signal processing is involved when compared to shallow seismic-reflection methods. Data collection is rapid and non-invasive, allowing profiles to be collected easily and quickly without altering a study site. The digital data collected are easily manageable on computer workstations with software developed for the petroleum industry to interpret seismic data. Collection of multiple profiles or three-dimensional grids of GPR data at study sites allows outcrop studies to be extended into the third-dimension, sometimes greatly enhancing understanding of stratigraphic architecture. Grids of GPR data can also be used to supplement and connect discrete core information.
Typical GPR frequencies for stratigraphic studies range from 10 to 100 MHz, resulting in vertical imaging resolutions of 1.5-1.0 m (4.9-3.3 ft). Although such resolution is sufficient for targets that are relatively large or laterally extensive, it may be insufficient for imaging detailed stratigraphy needed for some reservoir studies. Use of higher-frequency antennas (e.g., greater than 200 MHz) increases resolution enough to image fine-scale stratigraphic variations, but penetration depths decrease due to signal attenuation, which increases with frequency.
High-resolution ground-penetrating radar (GPR) is a subsurface imaging tool that can extend results gained from studies of reservoir-analog outcrops and add detailed information about reservoir analogs that is unavailable from either seismic data or well control alone. Integration of GPR-reflection information and outcrop photomosaics allowed detailed study of subtle changes in lithology and bedding surfaces by comparing lateral and vertical changes in GPR-reflection character with outcrop features. Outcrops are valuable for confirming interpretations of reflections and providing velocity information for the GPR data. Features as small as 0.1-0.2 m (0.3-0.7 ft)--including major sedimentary architectural elements and internal features such as fractures, internal bedding, and crossbedding have been imaged. Results to date indicate that GPR can be successfully used as an aid in outcrop studies to provide quantitative data for use in reservoir modeling (Martinez, Kruger, and Franseen, 1998).
Selected References
Martinez, Alex, Kruger, Joseph M., and, Franseen Evan K., Sept. 15, 1998, Utility of Ground-penetrating Radar in Near-surface, High-resolution Imaging of Lansing-Kansas City (Pennsylvanian) Limestone Reservoir Analogs, Published online Current Research in Earth Sciences, Bulletin 241, part 3. PDF (Portable Document Format).
Kruger, J.M.; Martinez, Alex; Berendsen, Pieter; and Shoemaker, M.K., 1995, A high-frequency ground-penetrating radar study of the Randolph kimberlites, Riley County, Kansas: Kansas Geological Survey, Open-file Report, no. 95-59, 51 p.
Kruger, J.M.; Martinez, Alex; and Franseen, E.K., 1996, A high-frequency ground-penetrating radar study of the Drum Limestone, Montgomery County, Kansas: Kansas Geological Survey, Open-file Report, no. 96-49, [Online: January 1997].
Martinez, Alex; Beaty, D.S.; Feldman, H.R.; and Kruger, J.M., 1996, Three-dimensional characterization of a fluvial sandstone reservoir analog in northeast Kansas using high-resolution ground-penetrating radar: Kansas Geological Survey, Open-file Report, no. 96-36, [Online: September 1996]
Martinez, Alex; Kruger, J.M.; and Franseen, E.K., 1995, A high-frequency ground-penetrating radar study of the Plattsburg Limestone and Bonner Springs Shale, I-435/I-70 interchange, southwest Wyandotte County, Kansas: Kansas Geological Survey, Open-file Report, no. 95-58, 52 p.
Martinez, Alex; Kruger, J.M.; and Franseen, E.K., 1995, A high-frequency ground-penetrating radar study of the Captain Creek Limestone, Johnson County, Kansas, Kansas Geological Survey, Open-file Report, no. 95-57, 23 pages
Martinez, A., A. Byrnes, D. S. Beaty, T. R. Carr, and J. M. Stiles, in review. Comparison of ground-penetrating radar response and rock properties in a sandstone-dominated incised valley-fill deposit: Geophysics.
Martinez, A., D. S. Beaty, J. Stiles, and T. R. Carr, 1998. Comparison of ground-penetrating radar reflectivity and rock properties in a sandstone-dominated incised valley-fill deposit: in Proceedings from the 7th international conference on ground-penetrating radar, 693-698.
Martinez, A., E. K. Franseen, and D. S. Beaty, 1998. Applications of ground-penetrating radar to sedimentologic and stratigraphic studies - examples from Pennsylvanian silciclastics and carbonates in Kansas: in Proceedings from the 7th international conference on ground-penetrating radar, 687-692.