--> Abstract: Geological and Seismic Forward Modeling of a Tidal Channel Outcrop Analog: Dry Wash, Upper Ferron Sandstone, Utah, by Mark Tomasso, Renaud Bouroullec, and Keumsuk Lee; #90078 (2008)

Datapages, Inc.Print this page

Geological and Seismic Forward Modeling of a Tidal Channel Outcrop Analog: Dry Wash, Upper Ferron Sandstone, Utah

Mark Tomasso1, Renaud Bouroullec2, and Keumsuk Lee1
1Bureau of Economic Geology, The University of Texas at Austin, Austin, TX
2Chevron Center of Research Excellence, Colorado School of Mines, Golden, CO

Tidal channel and associated shoreface deposits form reservoirs around the world. The Cretaceous Upper Ferron Sandstone of central Utah provides excellent outcrops of lower, middle, and upper shoreface deposits, coupled with deltas and tidal deposits. One such outcrop, at the Dry Wash locality, comprises a shallowing-upward sequence topped by tidal channel sandstones. This sequence is then capped by a transgressive ravinement surface followed by prodeltaic mudstones.

The tidal channel at Dry Wash crops out in 3-D around a series of roadcuts and dry valleys. The channel outcrop itself comprises a 20 m thick series of WNW-ESE striking lenticular sandstone and mudstone bar-forms that are interpreted to represent the inner bars of a northward migrating meander loop. Detailed photopanel interpretation and stratigraphic logging, coupled with the collection of lidar and ground-penetrating radar (GPR) data, allow a high-resolution spatially referenced geological model to be constructed at the element scale. Facies and petrophysical modeling of the geological model was carried out using correlated stratigraphic logs and regional facies trend information. Two seismic forward models at varying and combined peak frequencies were generated using the 3-D exploding reflector method, one for a shallow type (North American) reservoir, and one for a deep type (North Sea) reservoir.

Isopach maps for each individual bar illustrate the evolution of the channel through time. Results of the seismic forward models show that, whilst the top and base of the channelized unit can be picked, estimating facies relationships, even qualitatively, from amplitude data alone is hard. However, combination seismic attributes can be used to distinguish individual channel bars and net sand.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas