Seismic Characterization of Deep Illinois Basin Reservoirs as Possible Targets for Carbon Sequestration

John H. McBride¹, Hannes E. Leetaru², and R. William Keach^1
1Geological Sciences, Brigham Young University, Provo, UT
²Illinois State Geological Survey, University of Illinois, Champaign, IL

Assessing the feasibility of sequestration of carbon dioxide in deep saline reservoirs of the Illinois Basin (USA) has been guided largely by the mapping and analysis of 2D and 3D seismic reflection data. One of the primary issues for sequestration planning in this region is the detection and mapping of small-scale faults or other structural discontinuities at the target level near the Cambrian Mt. Simon Sandstone. Such discontinuities, which may affect the reservoir and its overlying sealing strata, must reliably be detected and mapped in three dimensions before a reservoir can be deemed suitable for sequestration. The Paleozoic strata in the Illinois Basin have been deformed by multiple episodes of tectonism; however, most of the deformation has produced relatively small displacements when viewed at conventional seismic scales. In this study, we test various techniques to enhance seismic interpretation of the structure of a small oil field, Tonti in the Illinois Basin. Techniques used include 3D spectral decomposition and semblance, combined with other seismic attributes, in order to demonstrate the crucial need for broad bandwidth data and 3D continuity-based seismic attributes when mapping the subtle structural discontinuities that characterize the basin. The results show that 3D seismic attributes can identify fault-related discontinuities at or near the sealing horizon (base of the Knox Group (Cambro-Ordovician; at or near the top of the Mt. Simon Sandstone)) whereas on conventional 2D seismic profiles these discontinuities are at best difficult or impossible to interpret as faults.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas