Fracture Properties From Seismic Scattering

Abstract

Fractures scatter seismic energy and this energy can be analyzed to provide information about fracture direction and density. Laboratory and numerical (finite difference) models of fractures show that scattered energy varies with the seismic acquisition direction relative to the orientation of parallel fracture sets. Data acquired normal to fracture strike displays forward and backscattered energy that is canceled in the stacking process, while data acquired parallel to the fracture strike contains forward scattered and guided waves that are enhanced by stacking. The Scattering Index method estimates the fracture orientation by comparing wavelet changes in the data from azimuthal stacks. Fracture density or spacing can be estimated by spectral methods that include f-k analysis of backscattered energy or analysis of spectral notches as functions of azimuth. Application of these methods to data from a fractured carbonate field results in fracture orientation and density estimates that are consistent with borehole measurements.