Seismic applications > Processing of a 3D shot point

In 3D, the elementary spread is a cross spread. An elementary cross spread is composed of a line of receivers and a line of sources. The receiver line and source line are perpendicular and cross in the middle. As for 2D, the shot points recorded for seismic surveys are usually corrupted by surface waves. For seismic imaging based on reflected waves, it is necessary to be able to separate weak reflected events from high energy surface waves. Wave separation is a crucial step in the processing sequence. The conventional F-K method is used to filter surface waves. The SVD method (Singular Value Decomposition) is then used to extract refracted waves. The different step of the processing sequence are: amplitude recovery, deconvolution by spectrum equalization, wave separation by SVD and F-K filters, normal move-out (NMO) with time variant velocity law and time to depth conversion.

The 3D shot point presented here is cross spread composed of 48 traces. The distance between 2 adjacent geophones is 2 m. The source is a weight dropper situated in the middle of the recording with a lateral offset of 45 m. The animation describes the different processing steps. At each step the data are shown both in the time- distance domain and in the frequency – wavenumber domain ( F-K domain).