A technique developed and perfected in France by Compagnie Generale de Geophysique makes it possible to record, process, and interpret reflected events originating from every direction.

The field layout is the same as that for conventional, multiple-coverage, seismic-reflection profiling. The only difference is that shot points are placed along oblique lines, so as to obtain several parallel, regularly spaced, depth-point lines. After processing, these lines yield comparable, although not identical, seismic sections, and a computer is able to analyze, by the cross correlation process, the slight shift of reflection events caused by lateral gradients.

A complete software was developed and the longitudinal dips, lateral dips, total dips, migration offsets, and time corrections are produced by a Calcomp plotter. The basic document is a section obtained by stacking the individual parallel sections after removing events which do not correlate laterally. The Calcomp displays provide the necessary parameters for migrating all events in three dimensions.

Considerable improvement over old methods was provided in tectonically complex areas. In other cases, an apparent unconformity resulted from 2 lateral events of opposite dips, a reflection on a fault plane beyond the seismic line was identified, and good results were obtained using lateral dip criteria in an area where high multiplication had been unsuccessful.

The advantage of wide-line profiling is that it expands the multiplication in lateral directions at a small cost increase. The software developed by CGG sorts out the seismic arrivals and provides tools for migration in a true three dimensional space.

The wide-line profiling technique has now reached the industrial stage and was used successfully in areas with complex structural geology, such as Spain, France, Italy, Libya, Angola, and Canada.

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