Predicting Fracture Orientations with Volumetric Curvature Gradient Analysis: Case Study from Teapot Dome in Wyoming
Seismic curvature gradient is a simple but useful high-order geometric attribute that evaluates local changes in the geometry of seismic reflectors, and has demonstrated its value for structure analysis, especially fracture prediction in fractured reservoirs. However, most recent efforts have been primarily focused on predicting fracture intensity by this attribute, but not on fracture orientations. The latter is crucial and essential for effective fracture characterization and modeling. This study extends the concept of curvature gradient to curvature-gradient azimuth and uses them to represent the principle value and principle direction of curvature gradient, respectively. Volume-based curvature gradient analysis is best achieved in a two-step process. First, we develop a computational equation for azimuthal curvature gradient that measures curvature gradient along any given azimuth in 3D space. Then, we implement an azimuth-scanning approach to find local maximums of curvature gradient. Such a technique allows us to simultaneously generate two volumes of curvature gradient and curvature gradient azimuth. We apply curvature gradient analysis to a fractured data set from Teapot Dome in Wyoming and find lineaments not observable with other seismic coherence or curvature attributes. Both the regional and cross-regional fractures are better delineated by our proposed method. Such a model indicates that in fractured reservoirs like Teapot Dome, faulting and fault-related folding contribute dominantly to the formation and evolution of fractures. The example demonstrates the potential of this new technology to predict mode and orientation of fractures in the reservoirs.
AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014