Skip to Main Content
Book Chapter

Structural and Stratigraphic Compartments in a Horizontal Well Drilled in the Eolian Tensleep Sandstone, Byron Field, Wyoming

By
N. F. Hurley
N. F. Hurley
Colorado School of Mines Golden, Colorado, U.S.A.
Search for other works by this author on:
A. A. Aviantara
A. A. Aviantara
The University of Tulsa Tulsa, Oklahoma, U.S.A.
Search for other works by this author on:
D. R. Kerr
D. R. Kerr
The University of Tulsa Tulsa, Oklahoma, U.S.A.
Search for other works by this author on:
Published:
January 01, 2003

Abstract

The Tensleep Sandstone is a major oil and gas producer in the Bighorn Basin, Wyoming. Cores, borehole images, and outcrop descriptions have been used to characterize the formation. Lithofacies include: (1) porous and permeable eolian cross-stratified units; (2) lower permeability, finely laminated interdune units; and (3) relatively impermeable marine carbonate and clastic units. Individual eolian dunes range in thickness from 2 to 10 m (6 to 30 ft), with first-, second-, and third-order bounding surfaces identified in outcrops, cores, and logs.

Byron field is a northwest-southeast-trending asymmetric anticline. In 1992, a medium-radius lateral hole was drilled from the southwest flank toward the crest of the fold. The horizontal well was cased from the surface to the top of the Tensleep Sandstone. The re-mainder of the well, which was drilled for approximately 150 m (500 ft) on an uphill slant, stayed in the uppermost Tensleep Sandstone in a 6-m- (20-ft-) thick stratigraphic interval. This part of the borehole was left uncased. The general shape of the borehole is that of a fishhook, where the structural high is at total depth.

Borehole-image log interpretation in the horizontal well showed two sets of roughly orthogonal fractures. Average spacing, corrected for borehole geometry, is 2.3 m (7.5 ft) for Set 1 fractures, which lie approximately perpendicular to the borehole path. Set 2 fractures, which lie roughly parallel to the borehole path, have a spacing corrected for borehole geometry of 0.9 m (3.0 ft).

Using prior knowledge of the paleowind direction, the horizontal well was drilled approximately perpendicular to the trend of the eolian dunes. Interpretations of bed boundaries suggest that the borehole crossed at least five eolian-facies architectural elements in 96 m (315 ft) of lateral distance. This suggests an average spacing of19 m (63 ft) for dune-related compartments. Outcrop and core studies show that flow barriers or baffles commonly exist at bounding surfaces between such compartments.

The last 46 m (150 ft) of the borehole was full of oil. The oil-water contact in the borehole, which was stable during several days of logging, may represent the height of the oil-water contact in the fractures. Note that this level is hundreds of meters (or feet) above the original oil-water contact in the intergranular porosity. This well suggests a novel but untested way to complete a horizontal well: (1) run tubing to total depth, and (2) use the borehole as a downhole oil-water separator. This completion technique could reduce water cuts and prolong the life of Byron field and other fractured reservoirs with strong water drives or active waterfloods.

You do not currently have access to this article.

Figures & Tables

Contents

AAPG Methods in Exploration Series

Horizontal Wells: Focus on the Reservoir

Timothy R. Carr
Timothy R. Carr
Search for other works by this author on:
Erik P. Mason
Erik P. Mason
Search for other works by this author on:
Charles T. Feazel
Charles T. Feazel
Search for other works by this author on:
American Association of Petroleum Geologists
Volume
14
ISBN electronic:
9781629810553
Publication date:
January 01, 2003

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal