Volume-based curvature computations illuminate fracture orientations — Early to mid-Paleozoic, Central Basin Platform, west Texas

Abstract

Volumetric curvature analysis is a simple but computationally intensive procedure that provides insight into fracture orientation and regional stresses. Until recently, curvature analysis has been limited to computation along horizon surfaces that may be affected by unintentional bias and picking errors introduced during the interpretation process. Volumetric curvature is best estimated in a two-step process. In the first step, we use a moving-analysis subvolume to estimate volumetric reflector dip and azimuth for the best-fit tangent plane for each sample in the full volume. In the second step, we calculate curvature from adjacent measures of dip and azimuth. We use larger curvature analysis windows to estimate longer wavelength curvatures. Such a technique allows us to output full 3D volumes of curvature values for one or more scales of analysis. We apply these techniques to a data set from the Central Basin Platform of west Texas and find lineaments not observable with other seismic attributes. These lineaments indicate that, in the lower Paleozoic interval, a left-lateral shear couple oriented due east-west controls the local stress regime. Such a model predicts that extension faulting and fractures will be oriented northeast-southwest. The example demonstrates the potential of this new technology to determine stress regimes and predict azimuths of open fractures.