High-resolution velocity models
Derive high-resolution velocity and anisotropy models from seismic data using a two-way wave equation.
WesternGeco has a broad portfolio of technologies targeted at detecting, quantifying, and compensating for azimuthal anisotropy. Interpretation of these analyses delivers detailed information on the anisotropy magnitude and directional variations. These, in turn, may relate to fracture density (fracture porosity) and orientation (directions of preferred permeability). Starting from the shallowest layer and working downward by layer stripping, we independently determine the anisotropy levels and correct for them during the processing sequence.
Shear waves are very sensitive to changes in azimuthal anisotropy, which may be induced by lithology, stress, or fractures because the shear wave is a transverse wave mode. Azimuthal anisotropy splits the reflected shear wave into two distinct orthogonal waves. This shear splitting, caused by changes in the subsurface, can be analyzed and compensated for in a layer-stripping approach using our pre- or poststack tools.
We offer a variety of both pre- and poststack tools for azimuthal anisotropy analysis using shear-wave information, including
Ocean bottom seismic (OBS) and land acquisition configurations let you record seismic data across a rich distribution of azimuths.
By splitting the data in limited-azimuth cubes, we can clearly analyze any azimuthal variations in P-wave amplitudes, velocities, and AVO effects.
In most basins, shale reservoirs are bounded by limestone and carbonates at the top and the base. Consequently the isotropic, boundary reflection coefficients are high. Also, shale is anisotropic with or without existing fractures and the anisotropy is high.