Western Atlas International, Inc.

Baker Hughes Corporation

Westerngeco L.l.p.

Compagnie Generale De Geophysique

Necati Gulunay

Ronald E Chambers

Coherency analysis, such as semblance scan or stacking amplitude, is used to locate diffractors. This is done utilizing traces of a recorded 3-D marine survey with one or more cables. Locations of each diffractor are determined by comparing the lateral coherency of the received amplitudes that each assumed diffractor position generates. Once the diffractors are located, noise energy originating from the diffractors is minimized.

Method for determination of diffractor locations at sea bottom for the purpose of attenuating such energy

Lines of existing data are extrapolated to provide additional lines of seismic data by using small inline gates of existing cables. At each frequency slice of a space gate on the existing cables, a 2-D prediction error filter that can predict the data in forward and backward directions is designed. A prediction filter is obtained from the prediction error filter and applied to a cable at an edge of the space gate to predict a first missing cable. By repeating this process using overlapping inline gates, overlapping inline gates of the extrapolated cables may be obtained. By suitable weighting of the inline gates of the extrapolated cables, a complete cable length is extrapolated. The process may be repeated using the first extrapolated cable in the derivation to give additional extrapolated cables. The invention may be used for interpolating cables of dealiased cables between existing cables using a masking and filtering operation in the frequency-wave number domain. In an alternate embodiment, existing lines of seismic data are sorted to give a crossline sort. The crossline sorted data are interpolated in the frequency-wave number domain to provide interpolated data between the lines of existing swaths of 3-D seismic data.

3-D seismic trace extrapolation and interpolation

Marine seismic data sets are generally under-sampled spatially because of the relatively long listening times required in deep water. It is customary to use very long spreads in the field thereby enhancing aliasing and interference from coherent noise. A seismic-signal data processing method is proposed that applies a combination of a forward parabolic Radon transform and a linear Radon transform to the data, followed by a further transform to a three-dimensional frequency domain. In this domain, a deterministic operator is applied to the data to sharpen the Radon-domain response thereof. The data are then scavenged of noise in the Radon domain and inversely transformed back into the time-space domain.

Reducing aliasing artifacts in seismic data processing using sharpened

A computer-aided method for providing a de-aliased output data set d.sub.L (t,x.sub.L,y.sub.L) from a spatially aliased, three-dimensional, input data set of known seismic signals, a(t,x,y), where L is an interpolator. The known data set is zero-padded by L. The zero-padded data set is zero-masked. The zero-padded data set is divided by a zero-padded, zero-masked data set to provide an interpolation operator H.sub.L. L-1 zero traces are interleaved between the known traces of data set a(t,x,y) to provide a zero-inserted data set c.sub.L ((t,x.sub.L,y.sub.L) whose transform is C.sub.L (m,k.sub.xL,k.sub.yL). The product of (H.sub.L) with (C.sub.L) is (D.sub.L) which is inverse-transformed to provide the desired de-aliased data set d.sub.L (t,x.sub.L,y.sub.L).

Unaliased spatial trace interpolation in the f-k domain

Sparsely spatially-sampled seismic time-scale trace gathers may be aliased for certain spatial and temporal frequencies. Aliasing may be avoided by application of a spatial interpolation scheme that uses the phase difference between the f-k phase spectra of the odd and the even traces to generate an interpolation operator in the f-k domain. The operator is multiplied point-by-point with the f-k transform of the original recorded trace gather. The resulting complex product is inverse transformed to the t-x domain whereupon the interpolated traces are interleaved between the original recorded traces to unwrap the aliased events.

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Missouri City, TX, United States of America

Necati Gulunay