3-D Geologic Modeling and Fracture Interpretation of the Tensleep Sandstone, Alcova Anticline, Wyoming

Nathaniel Gilbertson
Colorado School of Mines, Department of Geology and Geological Engineering
Golden, Colorado
[email protected]

The Alcova Anticline is a Laramide-age structure on the southeast margin of the Wind River Basin, central Wyoming. The Tensleep Sandstone, a prolific oil-producing reservoir, is well exposed along the trend of the anticline. The North Platte River cuts perpendicularly across the axis of the anticline, resulting in two near-vertical walls of Tensleep Sandstone. This provides an excellent location to describe and characterize the changes in frequency and orientation of fractures in the Tensleep Sandstone across the anticline. The emerging technology of outcrop scanning using Lidar will be utilized to aid in the quantification of fracture data.

Lidar is a high-resolution optical laser scanning system that can rapidly collect 3-D data for an outcrop. Scans of the two canyon walls will be acquired and placed into a 3-D geologic model constrained by field measurements. Fracture data, such as orientation, trace lengths, and intersections will be extracted from the Lidar dataset and used to populate the 3-D model with fractures of the same statistics.

This project will lead to a better understanding of fracture distribution, particularly in Laramide-age basement-involved structures. An accurate geologic model can help predict fracture patterns and intensities, which can then be entered into reservoir modeling software. These results can be applied to enhance recovery in existing Tensleep fields. Another application is for sequestration of carbon dioxide gas. The Tensleep has been identified as a potential storage site for carbon dioxide that would otherwise be vented to the atmosphere.

AAPG Search and Discovery Article #90033©2004 AAPG Foundation Grants-in-Aid