Study of PP-wave azimuthal reflection coefficients in fracture-induced TTI media

The fracture in shale is one of the most important research objectives of shale oil and gas reservoirs’ exploration and development. In seismic profiles, the resolution is considered as one-fourth of the seismic eigen wavelength. Fractures whose length are less than the resolution are usually shown as the azimuthal anisotropy of seismic travel times and amplitude. Media contain one set of tilted fractures that could be approximated as TTI media. For TTI media induced by tilted fractures, we proposed a process based on linear slip theory and anisotropic parameters, in which we could calculate azimuthal reflection coefficients by the characteristics of background media and fractures. We designed numerical tests to verify the accuracy of the process, and based on the process, we studied the influence of the polar angles and densities of fractures on the AVAZ characteristics of the induced TTI media. Compared with present methods, the proposed method could be conducted without the prior information about the anisotropy symmetry and orientation of the media and could directly calculate the azimuthal reflection coefficient of the fracture-induced media according to the characteristics of background media and fractures.