Fracture and Karst Features Affecting Reservoir Performance in a Mississippian Reservoir, Cheyenne County, Colorado

Kansas Geological Survey

KGS Open-file 2006-14



Core, log, and seismic data provide complementary information about the Spergen reservoir in Cheyenne Wells and Smoky Creek fields. Core and log data show that productive Spergen exhibits a variety of lithofacies and a wide range of matrix porosities. Production is not well correlated with matrix porosity, suggesting that another parameter controls well performance.


The detailed structure map of the BMS/KYS horizon obtained from the seismic data along with the Keyes isopach map from well tops indicates a drainage pattern suggestive of karst. While production is not directly related to overall structure and thickness of the Spergen, subtle karst features, such as solution-enhanced fractures aligned along structural trends, may impact production. Various oriented lineaments have been identified on seismic curvature maps and these lineaments may relate to compartment boundaries, closed fractures, and/or open fractures.




The authors would like to thank Mull Drilling Company for providing seismic and well data, Seismic Micro-Technology, Inc., Hampson-Russell Limited Partnership, and GeoPLUS Corporation for access to software, and for access to well data. KGS staff members John Doveton, Alan Byrnes, Saibal Bhattacharya, Tim Carr, and Martin Dubois provided insight and technical assistance. Funding for this work was provided by the U.S. Department of Energy under contract DE-FC26-04NT15504.




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Last Modified May 2006