Characterization of Seismically Imaged Pennsylvanian Ooid Shoal Geometries and Comparison with the Modern

W. Lynn Watney¹, Evan K. Franseen¹, Alan P. Byrnes¹, Richard D. Miller¹, Abdelmoneam Raef¹, Stacy L. Reeder², and Eugene C. Rankey^2
1 The University of Kansas, Lawrence, KS
² Rosenstiel School of Marine and Atmospheric Science, Miami, FL

A 4-D-seismic study (Hall-Gurney Field, Kansas) is focusing on imaging and monitoring injected carbon dioxide movement within a thin (~4 m) heterogeneous Pennsylvanian Plattsburg Limestone. The reservoir consists of a 16 km x 3 km ooid shoal complex that encompasses two to three stacked, shallowing-upward cycles. Based on well logs, the succession forms 1.6 to 3.2 km2 lobes of locally porous carbonate mantling a broad paleotopographic high. Although seismic similarity facies maps are averaged over the entire thickness of stacked oolitic deposits, the images appear to show sinuous to linear, isolated pods and apparent parabolic forms within the 1.2 km2 seismic image, which are similar to geometries of individual oolitic shoal complexes in the Modern. Variations in the oomoldic pore system and geometries of beds within the oolite bodies appear to be associated with amplitude patterns. Curvature attribute seismic maps also suggest structural lineaments that may have influenced the location of depositional and diagenetic lithofacies. Core, wireline log, and CO2 flood data incorporated into a refined geomodel are verifying the seismic results. Our ability to image facies and geometric aspects of ancient subsurface ooid complexes at a scale comparable to Modern ooid complexes provides the opportunity to develop quantitative algorithms to define and predict geomorphic, granulometric, and petrophysical properties combining Modern and ancient oolitic systems. Our long term goal is to evaluate and quantify the nature of variables that control similarities and differences between oolitic depositional systems to construct object-based 3-D models that can be used to populate reservoir models.