Marine vibrator directive source survey

Abstract

Marine seismic surveys, including ocean bottom surveys, utilizing marine vibrator arrays that are capable of being driven in anti-phase to produce a directional source gradient. Marine seismic surveys may include activating the vibrator array to emit a plurality of radiation patterns with at least a first radiation pattern that has a first notch at a take-off angle that is not close to vertical. Some marine seismic surveys included emitting directive wavefields from two or more simultaneous seismic source arrays, where the two or more seismic source arrays have a phase that changes from shot-to-shot to allow simultaneous source separation of the directive wavefields.

What is claimed is: 
     
         1 . A marine seismic survey method, comprising activating a vibrator array of two or more marine vibrators to emit a plurality of directive wavefields with at least a first directive wavefield that has a first notch at a take-off angle that is not close to vertical, and less than a maximum take-off angle of interest, and at least a second directive wavefield that does not have a notch at a take-off angle close to that first notch. 
     
     
         2 . The method of  claim 1 , wherein the first directive wavefield has a first notch at a take-off angle greater than about 5 degrees and less than 45 degrees, wherein the maximum take-off angle of interest is 45 degrees. 
     
     
         3 . The method of  claim 1 , wherein the plurality of directive wavefields are emitted at the same spatial location. 
     
     
         4 . The method of  claim 1 , wherein the plurality of directive wavefields are emitted at different spatial locations. 
     
     
         5 . The method of  claim 1 , wherein at least two of the plurality of the emitted directive wavefields overlap in time. 
     
     
         6 . The method of  claim 5 , further comprising locating receivers on the seafloor and using the receivers to record vibrations from the directive wavefields. 
     
     
         7 . The method of  claim 6 , wherein the recorded vibrations are processed to separate vibrations from different directive wavefields. 
     
     
         8 . The method of  claim 6 , wherein the recorded vibrations are processed to reconstruct crossline wavefields.