This study estimates the carbon storage potential of interbedded shales and carbonate rocks (cyclothems) in the Pennsylvanian Lansing and Kansas City groups (LKC) on the Cambridge arch in southwestern Nebraska. This effort is essential to the development of a CO2 storage strategy for the Integrated Midcontinent Stacked Carbon Storage Hub project as part of the Department of Energy–National Energy Technology Laboratory’s Carbon Storage Assurance Facility Enterprise initiative. We present a static earth (SE) model representing the 250-ft (76-m)-thick LKCs. This model is based on vintage (mostly pre-1970) well logs from the Sleepy Hollow field (Red Willow County, Nebraska) as well as a new (June 2019) stratigraphic test well drilled expressly for the purpose of the present study. Interpretations of advanced petrophysical logs and cores from this new well were crucial ingredients in the development of the geologic framework for SE model development. Gamma-ray (GR) logs readily differentiate carbonate and mudstone units within the LKC, allowing the differentiation of three GR facies for use in a facies model. Carbonate rock units, which are composed of multiple textures, were correlated across the field. We capture the heterogeneity of these carbonates during petrophysical modeling using effective porosity logs along with Gaussian random function simulation conditioned by the three-dimensional facies model. The SE model was used in computing carbon storage estimates for each LKC carbonate zone over an area of 1 mi2. In total, supercritical CO2 storage is estimated at 602,157 t/mi2 (232,494 t/km2) when using a deterministic saline storage efficiency factor of 0.1.

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