AAPG Bulletin, V. 84, No. 6 (June 2000), P. 830-849.

Combining Outcrop Data and Three-Dimensional Structural Models to Characterize Fractured Reservoirs: An Example from Wyoming¹

Peter H. Hennings,² Jon E. Olson,³ and Laird B. Thompson⁴

©Copyright 2000. The American Association of Petroleum Geologists. All rights reserved.
¹Manuscript received September 17, 1998; revised manuscript received August 9, 1999; final acceptance November 15, 1999.
²Mobil Technology Company, Box 650232, Dallas, Texas 75265-0232. Present address: Phillips Petroleum Company, 510A Plaza Office Building, Bartlesville, Oklahoma 74004; e-mail: [email protected]
³Department of Petroleum and Geosystems Engineering, Box X, University of Texas, Austin, Texas 78712.
⁴Mobil Technology Company, Box 650232, Dallas, Texas. Present address: Consultant, 3804 Wooded Creek Drive, Dallas, Texas 75244; e-mail: [email protected]
We thank Mobil Technology Company for enthusiastic support of this research and permission for publication. We are greatly indebted to Bob Ratliff of Paradigm Geophysical, Inc., for assistance in the construction and analysis of the three-dimensional structural model. We thank Steve Laubach at The University of Texas Bureau of Economic Geology for analysis of outcrop samples. We thank Mobil Exploration and Producing U.S. and Scitel Data Corporation for permission to publish seismic data. Chris Zahm, Don Stone, Martha Withjack, Jerry Kendall, Neil Hurley, and John Shaw provided thorough reviews that greatly improved the scientific content and readability of the manuscript.

ABSTRACT

Combining a detailed outcrop characterization of fracture and fault occurrence with attributes from a three-dimensional model of an anticlinally folded clastic reservoir body, we determine which characteristics of the structural form and evolution are most closely related to the development of important reservoir-scale structures. Our example reservoir body studied is the Frontier Formation 1 sandstone in Oil Mountain, an asymmetric anticline on the western flank of Casper arch in central Wyoming. The three-dimensional model of the structure was constructed using an iterative scheme designed to maximize interpretation accuracy and precision. The model was analyzed to determine the spatial variance in morphologic and kinematic attributes. Using a quantitative testing approach, we found that the intensity of tectonically produced fractures is closely related spatially to rate of dip change and total curvature, with the former having the strongest correlation. This folding is a low-strain process compared to tear faulting, which has the strongest spatial correlation to larger strains. The location and magnitude of these higher strain areas can be adequately predicted by three-dimensional restoration and forward modeling of the upper bounding surface of the reservoir body. We use these results to build a predictive model for fault and fracture distribution at Oil Mountain and to discuss how this approach can aid in the exploitation of analogous producing reservoirs.