AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Lidar-Integrated Outcrop Characterization of Blackhawk Formation, Wasatch Plateau, Utah: Towards Improved Fluvial Reservoir Modeling
(1) Earth and Environmental Sciences, University of New Orleans, New Orleans, LA.
(2) Earth Science and Engineering, Imperial College London, London, United Kingdom.
(3) Centre for Integrated Petroleum Research, University of Bergen, Bergen, Norway.
An improved understanding of channelized fluvial sandbodies as reservoirs requires robust documentation of (1) external sandbody geometry in 3D, (2) internal sandbody architecture, and (3) paleo-channel reconstruction parameters. By integrating LIDAR, outcrop (photomosaics, measured sections), and subsurface core data, this study is investigating the type and distribution of coastal-plain and fluvial depositional elements in the Cretaceous Blackhawk Formation in Cottonwood Creek, eastern Wasatch Plateau, Utah. The 3D distribution of channel sandbodies, which form the principal reservoir lithofacies, is being documented to improve prediction of sandbody connectivity, continuity and producibility within sand fairways in analogous fluvial reservoirs and prospects.
Helicopter-borne LIDAR data from six contiguous, steep and inaccessible cliff-faces (~ 18km2) were used to generate a virtual outcrop model draped by digital photos that documents fluvial element distribution (isolation vs. amalgamation) and connectivity (lateral vs. vertical), and aids in 3D visualization of sand fairways (amalgamated channel complexes) and flow barriers (laterally extensive overbank mudstones). Detailed sedimentologic documentation of behind-outcrop core provides additional control in mapping channelized sandbodies in 3D across the six cliff-faces. Individual sandbodies are c. 2-13 m thick, medium-grained, and contain predominant dune cross-stratification and subordinate ripple cross-lamination. Architectural element analysis demonstrates that key large-to-small scale heterogeneities are associated with alternating fluvial channel sandbodies and coastal-plain mudstones, various architectural elements like bar-accretion and crevasse splays, and with considerable facies variations within individual architectural elements. Initial paleohydraulic calculations constrain paleo-channel morphology: flow depth of 6-8 m, channel width of 90-130 m, channel belt width of 1200-1600 m, and moderate sinuosity (1.7). Each of these channel parameters progressively decreases towards the upper part of the Blackhawk Formation, suggesting a gradual decrease in stream competency with increasing distance from the coeval shoreline.