Acquisition design for 3-D converted waves

Donald C. Lawton

Converted-wave (P-SV) fold and offset distribution were evaluated for a 3C-3D seismic survey planned for a program in the United States. Several design options were tested, including those for a conventional 3D seismic program encompassing the same area over which multicomponent data are to be collected. Optimum parameters for the converted-wave 3D acquisition were found to be a straight-line swath shooting method with a source line separation of 1540 ft (~470 m), a receiver line separation of 1760 ft (~537 m), and shot and receiver intervals of 220 ft (~67 m). A brick shot pattern was found to improve the offset distribution for P-P coverage but had little effect on P-SV offset distribution. Because of maximum offset requirements, it is recommended that all 3-component receivers be live for all shots encompassing the multicomponent survey area and for shots extending approximately 1700-1800 ft (~550 m) beyond the boundary of this area. This acquisition design requires 378 3- component geophones ( 1134 channels) and a total of 800 shots.