Method and system for reducing effects of sea surface ghost contamination in seismic data

Abstract

An improved de-ghosting method and system that utilizes multi-component marine seismic data recorded in a fluid medium. The method makes use of two types of data: pressure data that represents the pressure in the fluid medium, such as sea water, at a number of locations; and vertical particle motion data that represents the vertical particle motion of the acoustic energy propagating in the fluid medium at a number of locations within the same spatial area as the pressure data. The vertical particle motion data can be in various forms, for example, velocity, pressure gradient, displacement, or acceleration. A spatial filter is designed so as to be effective at separating up and down propagating acoustic energy over substantially the entire range of non-horizontal incidence angles in the fluid medium. The spatial filter is applied to either the vertical particle motion data or to the pressure data, and then combined with the other data to generate pressure data that has its up and down propagating components separated.

Description

[0001]This application is a Reissue of U.S. patent application Ser. No. 09 / 936,863, filed 18 Sep. 2001, now U.S. Pat. No. 6,775,618, which is a U.S. National Phase of International Application PCT / GB00 / 01074, filed 21 Mar. 2000, which designated the U.S. and claims priority to G.B. Application No. 9906456, filed 22 Mar. 1999. More than one Reissue Application has been filed for the reissue of U.S. Pat. No. 6,775,618. The Reissue Applications are 11 / 501,195 and 12 / 264,784, which is a Divisional Reissue Application of Reissue Application 11 / 501,195.FIELD OF THE INVENTION[0002]The present invention relates to the field of reducing the effects of sea-surface ghost reflections in seismic data. In particular, the invention relates an improved de-ghosting method that utilises measurements or estimates of multi-component marine seismic data recorded in a fluid medium.BACKGROUND OF THE INVENTION[0003]Removing the ghost reflections from seismic data is for many experimental configurations equ...

AI Technical Summary

Benefits of technology

[0006]Thus, it is an object of the present invention to provide a method of de-ghosting which improves attenuation of noise from substantially all non-horizontal angles of incidence.

[0007]It is an object of the present invention to provide a method of de-ghosting of seismic measurements made in a fluid medium which improves attenuation of the ghost as well as downward propagating noise from substantially all non-horizontal angles of incidence.

[0008]Also, it is an object of the present invention to provide a method of de-ghosting which is not critically dependent on knowledge about the properties of the surrounding fluid medium as well as hydrophone / geophone calibration and coupling compensation.

Problems solved by technology

These filters are only good at wavenumbers smaller than the wavenumber where the pole occurs.

Hence, energy with low apparent velocities (for instance S-waves or Scholte waves at the seafloor) will not be treated properly.

Moreover, since they do not have a complex part, evanescent waves will also not be treated properly.

However, apart from the difficulty with poles and zeros at critical wave numbers, they also require knowledge about the principles of the immediate sub-bottom locations as well as hydrophone / geophone calibration and coupling compensation.

However, this technique is not effective when the angle of incidence is away from vertical.

Also, this technique does not completely correct for wide-angle scattering and the complex reflections from rough sea surfaces.

Additionally, its is believed that the OBC techniques described have not been used successfully in a fluid medium, such as with data gathered with towed streamers.

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