Evaluation of Knox Supergroup Dolostones as a Target for Carbon Dioxide Storage in Western Kentucky
Michelle A. Pittenger, Charles T. Feazel, Govert J. Buijs, Ray R. Reid, Paul W. Johnson, 2012. "Evaluation of Knox Supergroup Dolostones as a Target for Carbon Dioxide Storage in Western Kentucky", Great American Carbonate Bank: The Geology and Economic Resources of the Cambrian—Ordovician Sauk Megasequence of Laurentia, James Derby, Richard Fritz, Susan Longacre, William Morgan, Charles Sternbach
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Much like an exploration play, defining a carbon dioxide (CO2) storage target starts with understanding the subsurface. This requires the integration of all available data, from core descriptions to seismic interpretation. Unfortunately, in the areas and reservoirs not traditionally explored for oil and gas, these data are rare to nonexistent. The Cambrian–Ordovician Knox Supergroup dolostones of western Kentucky qualify as one of these types of potential injection targets. With a database of about 25 well logs, a loose two-dimensional (2-D) seismic grid, a few whole cores, and a few well tests, a geologic model of the Knox in western Kentucky was constructed to help understand the potential for CO2 storage in these rocks.
Initially, ideas for porosity development in the predominantly tight Knox dolostones were based on geologic models of the age-equivalent Ellenburger and Arbuckle Formations. In these formations, karsting plays a dominant role. Evaluation of several Knox whole cores, however, indicated only minor epikarst zones in intervals with very low porosity. Most of the porosity development is associated with large dolomite crystal-lined vugs that are interpreted to have precipitated from hydrothermal fluids. Borehole image logs also seem topoint toward vugs and fractures as significant contributors to porosity.
Interpreted core and log data were integrated with 2-D seismic interpretations to produce a geocellular model that was used for flow simulation of potential CO2 injection volumes and rates within the Knox Supergroup dolostones. Initial indications are that the Knox Supergroup dolostones have the potential to accept the large volumes of supercritical CO2 necessary for a CO2 storage site, although a significant number of wells may be required. To further assess this model, the Kentucky Consortium for Carbon Storage drilled a well in 2009 to test the CO2 injection capacity of the Knox Supergroup and potential secondary targets. Further evaluation of the sealing capacity of the overlying tight carbonates and shales was also done using whole cores taken in this test well to assess their ability to permanently contain injected supercritical CO2.
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Great American Carbonate Bank: The Geology and Economic Resources of the Cambrian—Ordovician Sauk Megasequence of Laurentia
The Great American Carbonate Bank (GACB) comprises the carbonates (and related siliciclastics) of the Sauk megasequence, which were deposited on and around the Laurentian continent during Cambrian through earliest Middle Ordovician, forming one of the largest carbonate-dominated platforms of the Phanerozoic. The Sauk megasequence, which ranges upwards of several thousand meters thick along the Bank's margin, consists of distinctive Lithofacies and fauna that are widely recognized throughout Laurentia. A refined biostratigraphic zonation forms the chronostratigraphic framework for correlating disparate outcrops and subsurface data, providing the basis for interpreting depositional patterns and the evolution of the Bank. GACB hydrocarbon fields have produced 4 BBO and 21 TCFG, mostly from reservoirs near the Sauk-Tippecanoe unconformity. The GACB is also a source of economic minerals and construction material and, locally, serves as either an aquifer or repository for injection of waste material. This Memoir comprises works on biostratigraphy, ichnology, stratigraphy, depositional facies, diagenesis, and petroleum and mineral resources of the GACB. It is dedicated to James Lee Wilson who first conceived of this publication and who worked on many aspects of the GACB during his long and illustrious career.