Migration is essential to seismic imaging. It is carried out by backward extrapolation of the wavefield registered on the observation surface. The quality of images depends on the accuracy of the wavefield reconstruction at interior subsurface points. From the theory based on the exact solution of the scalar wave equation it is known that, for accurate wave extrapolation, data must be obtained from an infinite observation surface. Limiting of migration apertures, which is inevitable in practice, leads to artefacts in extrapolated fields. The distortion they cause in 2D and 3D imaging is different. In 2D migration, the artefacts known as truncation effects are much weaker than the signals being extrapolated and for this reason attract no special attention. In 3D migration, diffractions caused by an aperture edge are stronger and may create serious problems. For a circular aperture, their amplitudes are comparable to the amplitudes of the signals themselves. The study of aperture diffractions is intended to help in the search for ways of either suppressing them efficiently or deliberately utilizing them in order to improve imaging.
In optics, diffractions by an aperture play a constructive role in image making. This research shows that the same may take place in seismic imaging.
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The use of diffraction imaging to complement the seismic reflection method is rapidly gaining momentum in the oil and gas industry. As the industry moves toward exploiting smaller and more complex conventional reservoirs and extensive new unconventional resource plays, the application of the seismic diffraction method to image sub-wavelength features such as small-scale faults, fractures and stratigraphic pinchouts is expected to increase dramatically over the next few years. “Seismic Diffraction” covers seismic diffraction theory, modeling, observation, and imaging. Papers and discussion include an overview of seismic diffractions, including classic papers which introduced the potential of diffraction phenomena in seismic processing; papers on the forward modeling of seismic diffractions, with an emphasis on the theoretical principles; papers which describe techniques for diffraction mathematical modeling as well as laboratory experiments for the physical modeling of diffractions; key papers dealing with the observation of seismic diffractions, in near-surface-, reservoir-, as well as crustal studies; and key papers on diffraction imaging.