Effectiveness of Wide Marine Seismic Source Arrays

Abstract

The use of wide source arrays in marine seismic surveys has become a topic of interest in the seismic industry. Although the primary motivation for wide arrays may have been to get more guns in a source array without increasing the inline array dimension, wide arrays can also provide the added benefit of suppressing side-scattered energy. Comparisons of common midpoint (CMP) stacks of data acquired offshore Washington with wide and conventional-width source arrays, however, show only small and sometimes inconsistent differences. These data were acquired in an area where side-scattered energy is a problem. Comparisons of unstacked data, however, show dramatic differences between the wide and conventional source array data. The disparity between the stacked and unstacked data is explained by analyzing the effective suppression of back-scattered energy by CMP stacking. In this survey area, the action of CMP stacking was so powerful in suppressing the broadside energy that the additional action of the wide array was inconsequential in the final stacked sections. In other areas, where the scattering velocity is comparable to the primary stacking velocity, wide arrays may provide some advantage. Because they can degrade cross-dipping primary events, wide arrays cannot be used indiscriminately. They should be consideredmore » a special purpose tool for attacking severe source-generated noise from backscattered waves in areas where the action of CMP stacking is insufficient.« less