Ellison, Amanda¹, Matthew Pranter¹, Rex D. Cole², Penny E. Patterson³
(1) University of Colorado, Boulder, CO
(2) Mesa State College, Grand Junction, CO
(3) ExxonMobil Upstream Research Company

ABSTRACT: Anatomy of a Point Bar: Outcrop Modeling Using Lidar Data of the Upper Cretaceous Williams Fork Formation, Piceance Basin, Colorado

The stratigraphic architecture and internal heterogeneity of fluvial deposits of the Upper Cretaceous Williams Fork Formation in the Piceance Basin of western Colorado affect the distribution and connectivity of reservoir-quality sand bodies. Analyses of the geometry, stacking, and internal heterogeneities of fluvial elements from well-exposed outcrops of the Lower William Fork Formation provide important analogue information to condition 3-D geologic models of similar subsurface petroleum reservoirs. This is especially important in low to moderate net-to-gross (<40%) fluvial systems such as the Lower Williams Fork Formation, because the lateral variation within fluvial deposits are often difficult to resolve and correlate using only subsurface data.
Detailed stratigraphic analyses of outcrops of the Lower Williams Fork Formation in Coal Canyon, near Grand Junction, Colorado, are conducted to characterize the internal complexity and connectivity of fluvial sand bodies at a sub-seismic scale. Detailed measured sections, photomosaics, and outcrop correlation panels capture the variation of channel geometry, stacking, and internal sedimentology. In addition, to enhance the field study, Lidar data (LIght Detection And Ranging) have also been acquired. Lidar is a high-resolution (cm-scale) digital elevation model (with light intensity data). Lidar images are used to define fluvial elements and bounding surfaces, and to extract dimensional data for sandstone bodies. Using a combination of outcrop photomosaics and interpreted Lidar images, key surfaces, stratigraphic architecture, and dimensional data are extracted and used to build and condition 3-D geologic models of analogous petroleum reservoirs to gain a better understanding of sub-seismic sand body connectivity and internal heterogeneity.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.