Marine vibrator tuneable array.

摘要

A method of reducing horizontally propagating pressure waves in marine seismic exploration to improve the signal-to-noise ratio at associated receivers and reduce interference at unassociated receivers, comprises providing marine vibrators (12,14,16,18) in an array with a given separation between each vibrator, so that horizontally propagating pressure waves from the vibrators which generally traverse the array are out-of-phase at most frequencies of vibration. The amplitude output from each vibrator varies with the output frequency of each vibrator to maximise the cancellation of out-of-phase pressure waves along the array. A receiver, which usually includes a plurality of hydrophones (34,36,38) disposed in a streamer (20), is spaced from the marine vibrators at a distance sufficient to establish the receiver as being in the far-field. The output of each of the marine vibrators is locked in phase and frequency with a known pilot signal so that downwardly propagating pressure waves are substantially unaffected. The overall effect is a narrowing of the radiation pattern of the pressure waves. The resulting radiation pattern effectively directs pressure waves downwardly toward an underwater land formation; and reduces horizontally propagating pressure waves which normally result in interference with marine seismic receivers.