Three Dimensional Visualization of Reservoir Outcrop Analogues Using Ground Penetrating Radar
G. C. Gaynor, G. A. McMechan, Jun Cai, and Xiaoxian Zeng
Outcrop-based 3-D models, which describe specific geometries of, and relationships between, reservoir flow units and barriers, are valuable, both in field development, and in forecasting field performance through simulation. Ground penetrating radar (GPR) provides a sampling technique for quantifying the 3-D geometry a connectivity of reservoir flow unit analogues at interwell scales. This technique provides the necessary third dimension to stratigraphic data that are usually confined to 2-D outcrop faces. Propagation, reflection, and attenuation of GPR signals are dependent on the dielectric and conductive properties of near-surface rock units. The GPR response is kinematically similar to that of conventional reflection seismic. Imaging and interpretation of GPR data can utilize techniques of seismic acquisition, processing, and display.
GPR surveys were performed to acquire detailed 2-D and 3-D data at several outcrops that are reservoir analogue sites in the Ferron Sandstone and the Blackhawk Formation in Utah. Multi-frequency (50, 100 and 200 MHz) radar data achieved penetrations of up to 20-25 m with resolutions of 10-25 cm. The GPR data provide detailed images of individual cross-stratified units, lateral accretion sets, coal-bearing heterolithic sequences, and larger-scale cut-and-fill erosion surfaces. These interpreted stratigraphic features correlate well with adjacent outcrop faces and provide the basis for a three-dimensional interpretation. Barriers and flow pathways at less than interwell scales can be identified using visualization software. These geometries are incorporated into reservoir models that provide insight into scale-up considerations and sub-surface flow unit geometries.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California