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Predicting Fracture Network Characteristics in Unconventional Plays in Frontier Basins Using 3-D Seismic Data and Structural Modeling


In structurally complex and tight reservoirs where the exploitation of fractures is important, accurate fracture network characterization in early stage exploration is key. Early stage exploration typically suffers from a lack of well control data from which fracture directions can be identified. This study will evaluate the role of various factors that control fracture formation such as Tectonic tectonic history, geometric evolution, and mechanical stratigraphy to devise a workflow that can provide the investigator with best possible prediction of fracture networks in frontier basins. This study uses 3D seismic data available from Crane Field, Williston Basin, to test whether post stack seismic analysis and structural modeling techniques can adequately characterize fracture networks around compressional structures with minimal well control. Fracture patterns are predicted, by three common commercially available software applications, for the middle member of the Bakken Formation. These are compared to the fracture patterns observed in the Cottonwood Canyon Formation (time equivalent, and analogous, to the Bakken member) on and around the Bighorn Mountains, as well as to Bakken core data. Regional fracture data was collected from outcrops and from the literature. The literature suggests three predominant regional directions in the Williston Basin. These are NW, NE and S-N. In addition to these trends, a strong E-W trend was observed in the outcrops of Cottonwood Canyon, Darby and Gros Ventre Formations in the study area. A standard curvature analysis does not predict all of these fracture trends, and other considerations must be made, including tectonic history, interplay between local and regional stresses and rotation of the pre-folding fracture sets with the evolution of the fold. The workflow for fracture prediction presented takes into account all of the above-mentioned factors to accurately predict fracture network characteristics in and around compressional structures using minimal well control data for calibration. The study points out the existing flaws in using certain attributes, in isolation, for fracture prediction in and around compressional structures. In addition, it emphasizes on using a set of attributes in combination with structural modeling to ensure accuracy in fracture prediction in early stage exploration of frontier basins, where well control is limited.