Offshore broadband air gun seismic source based on virtual and real depth combination

Abstract

The invention discloses an offshore broadband air gun seismic source based on virtual and real depth combination. The source comprises a main seismic source and N-stage auxiliary seismic sources, wherein a first wave of the first-stage auxiliary seismic source in the N-stage auxiliary seismic sources and a ghost wave of the main seismic source are completely counteracted at the far-field end, a first wave of the next-stage auxiliary seismic source and a ghost wave of the previous-stage auxiliary seismic source are completely counteracted at the far-field end, the auxiliary seismic sources areequivalent to air gun seismic sources set at a specific virtual depth, meanwhile, the main seismic source and the N-stage auxiliary seismic sources are designed to be air gun arrays with real depth combination, and first waves of air guns at different depths in the main seismic source are subjected to same-phase superposition by adopting a time-delay excited mode. According to the method, the low-frequency response is effectively improved, meanwhile, the frequency domain notch introduced by the virtual and real depth ghost waves is compensated, so that the design purpose of a broadband seismicsource wavelet is achieved.

Description

Technical field

[0001] The invention belongs to the field of air gun seismic source design, in particular to a marine broadband air gun seismic source based on a combination of virtual and real depth. Background technique

[0002] At present, the air gun seismic source commonly used at sea is composed of multiple air guns with different capacities at the same depth. The simultaneous excitation of multiple guns is used to achieve the in-phase superposition of the first wave, and at the same time, the difference in bubble oscillation period caused by the difference in capacity is used to offset the residual bubbles. When the first wave propagates to the sea surface, the polarity reverses to form a ghost wave. The existence of ghost waves at the seismic source causes the lack of some specific frequencies in the frequency domain, which reduces the resolution of seismic data, which is called the notch effect. In order to eliminate the notch effect, people propose to place the air gu...

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