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Tying Rock Properties from Core to Seismic Reflectivity in the Kaiparowits Plateau, Utah


Near-shore and shallow marine depositional systems are becoming increasingly important to understand due to the global hydrocarbon reserves held in such deposits. As resolution of seismic reflectivity profiles increases, concepts of sequence stratigraphy can be utilized on the high resolution seismic datasets to improve the interpretation of seismic in near-shore marine successions. The Cretaceous John Henry Member (JHM), located in the Kaiparowits Plateau of southern Utah, reveals excellent exposures of fluvial and tidally influenced shallow marine deposits and offers an excellent opportunity to improve our understanding of imaging similar subsurface petroleum reservoirs. Previous work in this area has been focused on outcrops along the edge of the plateau, including 24 scattered cores. In this study we link a newly acquired seismic line to laboratory derived rock properties from a 440 m core that is approximately 50 m from the primary seismic line. The goal of this study was to use these rock properties from core combined with forward modeling to improve interpretation of seismic reflection data in shallow and near-shore marine deposits. The resulting line was subsequently tied to nearby outcrop descriptions to facilitate further understanding of the JHM. In order to accurately correlate rock properties to seismic, 60 core plugs and 15 thin sections were extracted to represent the 12 lithofacies exhibited in the core (EP-25). Core bench-top measurements were conducted to obtain Vp, Vs, density, permeability and porosity. The rock properties and corresponding thin sections illuminate the impact of grain size, sorting, mineralogy and clay content on seismic reflection within similar environments of deposition. Two intersecting seismic surveys (7 km in the north-south direction and 2 km in the east-west) were acquired on the plateau using 40 Hz frequency; this produced high resolution seismic data to which the forward models were calibrated, and provided a template for detailed interpretation of the seismic line. The wide range of Vp values (1500-4000 m/s) in a highly heterolithic system, and the number of overlapping values elucidates the complications of interpreting these deposits in seismic profiles. Integrating core, seismic and outcrop data improves multi-scale synthesis of data, and contributes to a better understanding of how to interpret fluvial and shallow marine deposits by placing them within a regional stratigraphic framework.