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]More than one reissue applications have been filed for the reissue of U.S. Pat. No. 6,775,618, where this application Ser. No. 12 / 264,784, filed on Nov. 4, 2008 is a divisional reissue application of a co-pending U.S. reissue application Ser. No. 11 / 501,195, filed on Jun. 8, 2006, for the reissue of U.S. Pat. No. 6,775,618, which was a national phase application, Ser. No. 09 / 936,863, filed on Sep. 18, 2001 of an international application, Ser. No. PCT / GB00 / 01074, filed on Mar. 21, 2000, which claims priority of a GB application, S / N GB 9906456, filed on Mar. 22, 1999; and where U.S. reissue application Ser. No. 11 / 501,195 was issued as U.S. Pat. No. Re. 41,656 on Sep. 7, 2010.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 ...

AI Technical Summary

Benefits of technology

The present invention provides a method for reducing the effects of downward propagating reflected and scattered acoustic energy in seismic data. This method uses spatial filters that can improve attenuation of noise from non-horizontal angles of incidence and downward propagating noise from substantially all non-horizontal angles of incidence. The filters are not critically dependent on the properties of the surrounding fluid medium, and can be used with both pressure and vertical particle motion data. The filters can be efficient in separating up and down propagating acoustic energy over a range of non-horizontal incidence angles. The method can be implemented robustly and efficiently, and can improve the resolution of pressure, velocity, and pressure gradient measurements.

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 properties 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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