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.

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