Generating seismic event using a sub-array of sources which is closest to a predetermined desired firing position

摘要

An array of seismic sources for generating seismic events comprises several (eg six to ten) linear sub-arrays (see figure 1), typically towed behind a vessel. Each sub-array has air guns 22-28 suspended from a float 19. A GPS device 34 on each sub-array allows the position of the sub-array to be determined. One of the sub-arrays is identified as being the sub-array closest to a predetermined desired firing position. The air guns in this sub-array, along with the guns in the arrays on either side, are then fired to generate a seismic event. This method and apparatus finds application in 4D (time-lapse) seismic surveys, as accurate positioning of the seismic source is required to avoid feathering.