Diffraction Imaging

Diffractions in seismic data often correspond to local heterogeneities in the subsurface, such as boulders, small gas pockets, and faults. These heterogeneities are in many cases the sources of risk for offshore construction, such as windfarm installation. So, the imaging of the diffracted wavefield may be useful in risk assessment.

RadExPro includes a set of tools for diffracted wavefield analysis.

Separation of the diffracted wavefield

The first step in any diffraction imaging workflow is the separation of the diffracted wavefield. The Structural Smoothing module helps the user to separate diffracted and reflected wavefields from each other, thus enabling further analysis of the diffracted component.

Original seismic data (left), estimated reflections (center) and diffractions (right)

Migration of the diffracted wavefield

Migration of the diffracted wavefield is the next step of a diffraction imaging workflow. There are several options for migration in RadExPro, including Stolt migration, Pre- and Post-Stack Kirchhoff time migration, and T-K migration. After the migration of the diffracted wavefield, various attributes can be computed, such as diffraction energy, and diffraction semblance.

Migrated diffracted wavefield (left) diffraction energy (center), and diffraction semblance (right)

One can observe that the amplitude maxima on these diffraction attributes correspond to the true locations of the heterogeneities which cause the diffractions. This can be demonstrated by overlaying one of these attributes over the original and migrated seismic images (the overlay was done outside of RadExPro). This makes the attributes useful for the studies of small-scale heterogeneities and risk assessment.

Diffraction energy overlayed over original (left) and migrated (right) seismic data.