Pgs Geophysical As

Hocine Tabti

Tilman Kluever

Øyvind Hillesund

Anthony James Day

Tilman Klüver

Neil Turnbull

David Helmer Carlson

Oyvind Hillesund

This disclosure is directed to methods and systems to evaluate noise contend of seismic data received during a marine survey. The seismic data includes pressure and particle motion data generated by collocated pressure and particle motion sensors of a seismic data acquisition system. The pressure and particle motion data are cross ghosted and temporal and spatial wavelet transforms are applied to the cross-ghosted pressure and particle motion data in order to compute pressure energies and particle motion energies in temporal and spatial scales of a temporal and spatial scale domain. The pressure and particle motion energies may be compared to evaluate noise content in the pressure and particle motion data, evaluate changes in the noise content during the marine survey, and adjust marine survey parameters to reduce the noise content.

Methods and systems to evaluate noise content in seismic data

The present disclosure is related to estimation of a far field signature in a second direction from a far field signature in a first direction. For a number of source elements, where the number of source elements corresponds to a seismic source, an impulse response in a first direction and a second direction can be determined. A transfer function that transforms a far field signature of the seismic source in the first direction to a far field signature of the seismic source in the second direction can be determined based on corresponding impulse responses in the first direction and the second direction. An estimated far field signature for the seismic source in the second direction can be determined based on the transfer function.

Estimation of a far field signature in a second direction from a far field signature in a first direction

Methods and systems to determine ghost operators from marine seismic data are described. Methods and systems extract statistical information about the free surface from N gathers of pressure and vertical velocity data obtained for N activates of a source. Ghost operators are calculated from the N gathers of pressure and vertical velocity data. The ghost operators may be used to characterize the actual source and receiver ghosts recorded in the seismic data, compute properties of the free surface, such a reflection coefficient and root mean square free surface height, and may be used to deghost pressure and vertical velocity data.

Methods and systems to determine ghost operators from marine seismic data

A marine seismic streamer includes at least one particle motion sensor array. The array includes a plurality of particle motion sensors disposed at spaced apart locations along the streamer. Outputs of the particle motion sensors are functionally coupled to form an array. A number of the particle motion sensors and a spacing between adjacent particle motion sensors are selected to attenuate noise in a selected mode of propagation and within a selected wavenumber range. The streamer includes means for weighting a signal output of each particle motion sensor in the at least one array. A signal weight applied to each sensor by the means for weighting is selected to optimize attenuation of the noise.

Array grouping of seismic sensors in a marine streamer for optimum noise attenuation

A method for determining upgoing pressure components of seismic signals from signals detected by combined pressure responsive sensors and motion responsive seismic sensors disposed in a plurality of laterally spaced apart streamers includes determining a threshold time at which angle of incidence error in the motion responsive signals in the cross-line direction falls below a selected threshold. Below the threshold time, the motion responsive signals are corrected for angle of incidence in the in-line and cross-line directions. Above the threshold time, the motion responsive signals are corrected for angle of incidence only in the in-line direction. Both sets of incidence corrected measured motion responsive signals, and the pressure responsive signals are used to determine upgoing or downgoing pressure components or upgoing or downgoing motion components of the measured motion responsive and pressure responsive seismic signals.

Method for optimum combination of pressure and particle motion sensors for a 3-D spread of dual-sensor marine seismic streamers

A method for using signals measured by pressure responsive seismic sensors and motion responsive seismic sensors disposed in a seismic cable includes simulating a selected range frequency response of the motion responsive sensor signals for each of a plurality of selected depths in a body of water. For each sensor position along the streamer, the one of the simulated selected frequency range responses is selected for which the selected depth most closely matches an actual sensor depth. The selected simulated selected range frequency responses are combined with the measured motion responsive sensor signals to produce full bandwidth motion responsive signals. The full bandwidth signals are combined with the pressure responsive signals to determine at least one of an upgoing and downgoing pressure or motion wavefield.

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Oslo, Norway

Hocine Tabti