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3-D Geocellular Modeling as a Tool for Understanding Very Large Scale Stratigraphic Architecture and Stacking Pattern in the Cretaceous of Central Utah, USA

Howell, John 1; Knudsen, Turid A.2
1 CIPR, University of Bergen, Bergen, Norway.
2 Norwegain Petroleum Directorate, Stavanger, Norway.

The Cretaceous strata which crop out around the San Rafael Swell in central Utah include up to 2500 m of Turonian to Campanian shallow marine and coastal plain deposits, laid down on the western edge of the epiric seaway that occupied the Sevier foreland basin. The deposits have been sub-divided into 4 large scale depositional cycles which include the Ferron, Emery, Star Point and Blackhawk formations of the Mesaverde Group.

Numerous studies have addressed the stratigraphic architecture of the individual units, but little work has been done to understand the large scale stratal architecture. The aim of this study has been to utilise reservoir modeling technology to represent, in 3D, the large scale stratal and facies architecture of the Mesaverde Group in this area.

The 2500 m thick model covers an area of 16,000 square km, with a lateral grid resolution of 1 x 1 km and a vertical resolution of 1- 5 m. It contains 64 million cells in 60 zones. The individual zones represent the shallow marine parasequences and their correlative offshore and coastal plain deposits. Facies associations have been modeled within each zone. The model has been conditioned to outcrop data, published literature, geological maps and a large virtual outcrop that was built by draping aerial photographs on to a terrain model.

Such large scale aspects of depositional systems have not typically been considered in this way, being more traditionally represented in 2D maps and cross sections. Building 3D geocellular models of such a large area provides an alternative method for better understanding the stratigraphic architecture. The results of the study demonstrate that models of such a scale can be used to quantifying aspects such as shoreline trajectories, which are not achievable by more conventional methods.

 

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