HOWELL, JOHN, DAVID HODGETTS, PETER BURGESS and STEPHEN FLINT, Strat Group, University of Liverpool, UK

Abstract: The Blackhawk Formation of Eastern Utah: Application of a High Quality Outcrop Dataset to Calibrate Modelling Studies

Sequence stratigraphic and quantitative geometrical studies of high quality outcrop datasets remains one of the best methodologies for understanding reservoir architecture. Thorough utilization of outcrop datasets can enable predictive variations in architecture to be interpreted from limited subsurface datasets, consequently reducing geological uncertainties. However, as no two depositional systems are identical, it is insufficient to simply extract numerical data without a proper understanding of the underlying driving mechanisms behind stratal architecture. The Cretaceous Blackhawk Formation of Eastern Utah provides a superbly exposed section through a shallow marine clastic wedge. A dataset, which includes a 120 km correlation panel and over 50 subsurface well logs formed the basis for modelling studies. Forward modelling of the quantified stratigraphic architecture enables the effects of altering individual controlling parameters, such as eustasy, tectonics or sediment supply, to be investigated. Using SMUT, a purpose built geometrical modelling package, the Book Cliffs stratal architecture was accurately recreated, including the progradational parasequence stacking patterns and the detachment associated with documented lowstand deposits.With well-documented stratal geometries and sonic velocities from comparable facies within the Middle Jurassic Brent Group reservoirs of the North Sea it has been possible to produce synthetic seismic lines for the Blackhawk Formation, using both simple ray tracing and a more complex wavefront modelling method. It is possible to model the seismic expression of known geometries, to test the sensitivities of seismic resolution.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England