Pgs Geophysical As

Walter Söllner

Okwudili Chuks Orji

Endrias Getachew Asgedom

Stian Hegna

Rune Tønnessen

Gregory Ernest Parkes

Elsa Cecconello

Martin Widmaier

Pierre Turquais

Gregg E Parkes

Norman Daniel Whitmore, Jr

Daniel Martin Lewis Barker

Xiao-Ping Li

Mickael Bastard

Endrias Getashew Asgedom

Alba Ordoñez

Charles Lameloise

Rune Tonnessen

Steve Bishop

Okwudili Orji

A proposed geometrical distribution for a first non-impulsive source and a second non-impulsive source of a source array can be received. A near-field-to-notional computation can be performed for the proposed geometrical distribution to yield a respective computed notional output of the first and second non-impulsive sources. Whether the computed notional output of the first non-impulsive source has a first amount of residue greater than a threshold amount of residue can be determined. Whether the computed notional output of the second non-impulsive source has a second amount of residue greater than the threshold amount of residue can be determined. An indication whether either of the first or second amounts of residue is less than or equal to the threshold amount of residue can be provided.

Geometrical distribution for non-impulsive sources

Processes and systems described herein are directed to performing marine surveys with marine vibrators that emit orthogonal coded pseudo-random sweeps. In one aspect, coded pseudo-random signals are generated based on coded pseudo-random sequences. The coded pseudo-random sequences are used to activate the marine vibrators in a body of water above a subterranean formation. The activated marine vibrators generate orthogonal coded pseudo-random sweeps. A wavefield emitted from the subterranean formation in response to the orthogonal coded pseudo-random sweeps is detected at receivers located in a body of water. Seismic signals generated by the receivers may be cross-correlated with a signature of one of the orthogonal coded pseudo-random sweeps to obtain seismic data with incoherent residual noise.

Mitigating residual noise in a marine survey with orthogonal coded pseudo-random sweeps

Processes and systems described herein are directed to imaging a subterranean formation from seismic data recorded in a marine survey with moving marine vibrators. The marine vibrators generate random sweeps with random sweep signatures. Processes and systems generate an up-going pressure wavefield from measured pressure and vertical velocity wavefield data recorded in the marine survey and obtain a downgoing vertical acceleration wavefield that records source wavefields, directivity, source ghosts, and random signatures of the random sweeps. The downgoing vertical acceleration wavefield data is deconvolved from the up-going pressure wavefield to obtain a subsurface reflectivity wavefield that is used to generate an image of the subterranean formation with reduced contamination from source wavefields, directivity, source ghosts, and random signatures of the random sweeps.

Seismic imaging with source deconvolution for marine vibrators with random source signatures

Processes and systems for generating images of a subterranean formation from recorded seismic data obtained in a marine survey are described. Processes and systems compute reverse-time receiver-motion-corrected upgoing and downgoing pressure wavefields at different locations of corresponding upgoing and downgoing observation levels based on the recorded seismic data. The reverse-time receiver-motion-corrected upgoing and downgoing pressure wavefields are time forwarded and extrapolated to obtain a corresponding receiver-motion-corrected upgoing and downgoing pressure wavefields at locations of a static observation level. An image of the subterranean formation is generated based at least in part on the receiver-motion-corrected upgoing pressure wavefield and the receiver-motion-corrected downgoing pressure wavefield.

Processes and systems for correcting receiver motion and separating wavefields in seismic data recorded with multicomponent streamers

Processes and systems are described for generating an image of a subterranean formation from seismic data recorded during a marine survey that employed a moving vibrational source. Processes and systems compute an up-going pressure wavefield from pressure data and vertical velocity data recorded in the marine survey. A direct incident downgoing vertical velocity wavefield that includes Doppler effects created by the moving vibrational source and characterizes a source wavefield and source ghost of the moving vibrational source is computed and deconvolved from the upgoing pressure wavefield to generate a subsurface reflectivity wavefield. The subsurface reflectivity wavefield is effectively free of contamination from the source wavefield, the source ghost, and the Doppler related effects. Processes and systems generate an image of the subterranean formation based on the subsurface reflectivity wavefield, thereby enhancing resolution of the image by attenuating the source-motion effects, source signature, and source ghost of the moving vibration source.

Correction of source motion effects in seismic data recorded in a marine survey using a moving source

Survey design for data acquisition using marine non-impulsive sources can include operating a first marine non-impulsive source at over a first frequency range for a first sweep length and operating a second marine non-impulsive source over a second frequency range for a second sweep length. The first sweep length can be based on available geological information of a subsurface location that is a target of a marine seismic survey, an intended speed of a marine survey vessel, and the first frequency range. The second sweep length can be based on the available geological information, the intended speed, and the second frequency range.

Survey design for data acquisition using marine non-impulsive sources

Processes and systems for deblending blended seismic data with attenuated source signatures and source ghost are described. Processes and systems compute blended upgoing pressure wavefield based on blended pressure wavefield and blended vertical velocity wavefield recorded in a marine survey of a subterranean formation. Downgoing vertical velocity wavefield is computed based on near-field pressure wavefields generated by source elements of sources activated in the marine survey. Deblended wavefield is computed based on the blended upgoing pressure wavefield and the downgoing vertical velocity source wavefield. The deblended wavefield may be used to generate an image of the subterranean formation with the source signatures and source ghosts contained in the blended pressure wavefield and blended vertical velocity wavefield.

Processes and systems that deblend and attenuate source ghosts and source signatures in recorded seismic data obtained in a marine survey

Processes and systems for deblending blended seismic data with attenuated source signatures and free-surface effects are described. The blended seismic data may have been recorded in a marine survey in which multiple sources are activated in the body of water above a subterranean formation. Receivers record overlapping pressure and vertical velocity wavefield responses from the subterranean formation as corresponding blended pressure wavefield and blended vertical velocity wavefield. Processes and systems compute an upgoing pressure wavefield and a downgoing vertical velocity wavefield based on the blended pressure wavefield and blended vertical velocity wavefield. Deblended primary pressure wavefields are computed based on the upgoing pressure and downgoing vertical velocity. The deblended primary pressure wavefields may be used to generate images of the subterranean formation that are substantially free of source signatures and free-surface effects.

Processes and systems that attenuate source signatures and free-surface effects in recorded seismic data

Parameters of a sweep signal that controls operation of a marine non-impulsive source can be set. Setting the parameters can include selecting a stop frequency of the sweep signal, defining a taper of the sweep signal, and adjusting an initial phase of the sweep signal. The parameters can be set such that a magnitude of an amplitude spectrum of a combined output of a marine impulsive source and the marine non-impulsive source is greater than or equal to a magnitude of an amplitude spectrum of a marine impulsive source output at frequencies below the stop frequency. A controller of the marine non-impulsive source can be programmed with the sweep signal having the parameters set to control the marine non-impulsive source.

Sweep signal for combination of a marine non-impulsive source output with a marine impulsive source output

This disclosure is directed to processes and systems that generate enhanced-resolution seismic images by interpolating sparsely recorded seismic data. Structured dictionary learning is employed to train a set of basis vectors, called 'atoms,' and corresponding sparse coefficients on patches of the recorded seismic data. The atoms are constrained to represent the geometric structure of reflection events in the recorded seismic data gather. Linear combinations of the atoms are used to compute interpolated patches over a finer receiver-coordinate grid. The interpolated patches replace the original patches in the recorded seismic data to obtain interpolated seismic data that can be used to generate an image of the subterranean formation.

Methods and systems to interpolate seismic data

Determining a far field signature of a source array can include receiving data associated with a sea surface state and determining a coherent portion and an incoherent portion of a reflection coefficient of the sea surface based on the received data. A notional source signature of each source of the source array can be determined based on the coherent portion, the incoherent portion, and near field data associated with each of the sources, and the far field signature of the source array can be determined based on the notional source signatures of each of the sources. The notional source signature and the far field signature can be stored. A seismic image of a subsurface location can be generated based on the determined far field signature.

Far field signature determination

The current disclosure is directed to methods and systems to determine properties of a subterranean formation located below a body of water. The methods and systems compute synthetic pressure and velocity vector wavefields that represent acoustic energy interactions within a model environment that comprises a model body of water located above a model subterranean formation. The model environment is separated into a stationary region and a time-varying region. The methods and systems include determining properties of the subterranean formation by iteratively adjusting the model environment to approximate the actual subterranean formation. The model environment is iteratively adjusted until a minimum difference between the synthetic pressure and velocity vector wavefields computed for each change to the model environment and actual pressure and velocity wave fields obtained from a marine seismic survey of the subterranean formation is achieved.

Methods and systems to determine properties of a subterranean formation

Methods and Systems for extrapolating wavefields while avoiding disruptions due to spatial aliasing are disclosed. Pressure wavefields measured with pressure sensors and vertical and horizontal velocity wavefields measured with three-axial motions sensors may be spatially aliased in at least one horizontal direction. The pressure wavefield and/or the vertical velocity wavefield are decomposed into one of an up-going wavefield and a down-going wavefield. The up-going or down-going wavefield is extrapolated using an extrapolator that depends on components of a slowness vector. In order to avoid disruptions in the extrapolated wavefield due to spatial aliasing, the components of the slowness vector are calculated from the measured pressure wavefield and the two horizontal velocity wavefields.

Methods and systems for extrapolating wavefields

Methods and systems that compute an approximate vertical-velocity wavefield based on a measured pressure wavefield and knowledge of the free-surface shape when the pressure wavefield was measured are described. The measured pressure wavefield is used to compute an approximate frozen free-surface profile of the free surface. The approximate frozen free-surface profile and the measured pressure wavefield are then used to compute an approximate vertical-velocity wavefield that does not include low-frequency streamer vibrational noise. The approximate vertical-velocity wavefield and measured pressure wavefield may be used to separate the pressure wavefield into up-going and down-going pressure wavefields.

Methods and systems that determine a velocity wavefield from a measured pressure wavefield

Denoising seismic data can include extracting a first plurality of overlapping patches corresponding to a respective seismic data window selected from a plurality of seismic data windows, reshaping the first plurality of overlapping patches into patch vectors, and determining sparse approximations of the patch vectors based on a dictionary and a sparse coefficient vector. Denoising seismic data can also include reshaping the sparse approximations into a respective second plurality of overlapping patches, and constructing a denoised version of at least one of the plurality of seismic data windows using the respective second plurality overlapping patches.

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Oslo, Norway

Walter Söllner