Post-stack attribute-based fracture characterization: A case study from the Niobrara shale

The ability to determine the relative density and orientations of fractures in potential reservoirs has become increasingly important as resource plays are now a major exploration and development focus for energy companies worldwide. Techniques have been developed using pre-stack data and velocity anisotropy to identify and map fractures. Azimuthal AVO has been employed to estimate fracture density and quantitatively assess how well this approach predicts reservoir quality (Hunt, 2010). Additionally, a new approach to quantitative azimuthal inversion for stress and fracture detection has been developed (Mesdag, 2016). This paper focuses on extracting a relative fracture density attribute and fracture orientations from migrated post-stack 3D seismic volumes. The detection and mapping of fractures in migrated poststack 3D seismic data depends on the resolution and signal-tonoise ratio of the data in the seismic volume. A discussion of resolution problems and the limits of resolution in post-stack 3D seismic data, and structurally-oriented post-stack coherent and random noise filtering is followed by descriptions of a Fracture Density attribute and of the extraction of fracture orientations. An example of the results of applying these processes and workflow is included from the Niobrara shale play in the United States.