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Stratigraphic Architecture and Evolution of a Sinuous Tidal Channel: Dry Wash, Cretaceous Upper Ferron Sandstone, Utah

Bouroullec, Renaud 1; Tomasso, Mark 2
1 Geology and Geological Engineering, Colorado School of Mines, Golden, CO.
2 Enhanced Oil Recovery Institute, University of Wyoming, Laramie, WY.

Tidal sandstone reservoirs are important targets in many producing basins (i.e. offshore Norway, Maracaibo Basin, Venezuela; Triassic of Alberta). The Cretaceous Upper Ferron Sandstone in Utah provides excellent outcrops of shoreface, deltaic and tidal deposits. The Dry Wash outcrop displays a shallowing upward sequence that includes a sandy heterolithic tidal channel exposed on multiple cliff faces. The sedimentary facies and architecture of the studied tidal channel were obtained using conventional and digital techniques. The data comprise 16 detailed measured sections, 7 interpreted photopanels, paleocurrent data, 2-D and 3-D ground-penetrating radar (GPR) profiles and multiple ground-based lidar scans. The dataset was co-visualized in Petrel and used to generate a high-resolution 3-D geological model. This model was also used to generate seismic forward models at several peak frequencies that underwent spectral recomposition for comparison back to real-world seismic images.

The channel shows 12 lateral accreting bar-forms comprised of well sorted medium-grained sandstone and mudstone bedsets. The accretionary sandy bar-forms are sigmoidal, imbricated, offlapping, and show amalgamated and non-amalgamated geometries. They are encased in abandonment facies composed of bioturbated carbonaceous mudstones and fine- to very fine-grained sandstone containing coal fragments. The accretionary sandstone bed sets contain planar tabular and trough cross-stratification bound by inclined erosive accretionary surfaces. The bar-forms represent the inner bars of a migrating meandering channel bend. Structure maps of key surfaces and isopach maps of the main intervals show: (1) a seaward channel migration, (2) a clockwise channel rotation, and (3) an increase of channel bend amplitude through time. The 3D geological model shows a complex intra channel longitudinal migration of bar-forms that are related to the geometry of the container and the tidal dynamics. The thickest sandy parts of the preserved strata are located downdip of the channel bend whilst muddy facies accumulate updip of the bend.

This study can be used to decrease uncertainty in tidal channel reservoir characterization by relating channel geometry/evolution to sandy channel fill location and migration.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009