Intra Source Array Offset and Static Difference Compensation by Optimal Vibrator Sweeping

During a seismic reflection measurement vibrators are used in groups, where all the members emit the same sweep simultaneously. Since there are small offset differences within the source array (the vibrators cannot be placed at exactly the same location and the pattern of vibrators provides filtering of coherent noises) the recorded signals are distorted by the slightly different arrival times of the individual vibrator signals. Also intra array static differences exist due to the changing properties of the nearsurface. These effects can be observed in the loss of energy, which is more pronounced at higher frequencies. For a seismic survey we can calculate optimal sweep start delay times for each vibrator within the vibratory group at each vibrator position. These optimal start delay times are applied to control the vibrators’ sweeping during the field acquisition. We show, that down to a target depth, the signal summation is improved and there is less high frequency loss, the resolution increased. We have also investigated the dependency of the arrival time differences on the survey parameters and the frequency-amplitude decay phenomena. The suggested method could give more signal amplitude at high frequencies with no special effort compared to the conventional technique.