Pgs Geophysical As

Anthony James Day

Tilman Klüver

Stian Hegna

Gregory Ernest Parkes

Martin Widmaier

Neil H R Turnbull

Christian Wilhelm Strand

Tilman Kluver

Hocine Tabti

Thorbjorn Rekdal

Neil Hugh Turnbull

Neil Hugh Richard Turnbull

Variable depth multicomponent sensor streamer. At least some of example embodiments including perform a geophysical survey by: setting a first target depth for first depth positioning device of a sensor streamer, the first depth positioning device associated with a first sensor of the sensor streamer, the first sensor at a first offset, and the first target depth based on tension in the sensor streamer proximate the first sensor; setting a second target depth for a second depth positioning device of the sensor streamer, the second depth positioning device associated with a second sensor of the sensor streamer, the second sensor at a second offset greater than the first offset, the second target depth based on tension in the sensor streamer proximate the second sensor, and the second target depth greater than the first target depth; towing the sensor streamer through the water; and obtaining data from the sensors.

Variable depth multicomponent sensor streamer

Computational systems and methods that combine global frequency-wavenumber-domain ('f-k domain') filters with localized eigenimage based event selection to generate a resulting wavefield with reduced filter imprints on gather edges, reduced noise, and correct treatment of aliased energy are disclosed. The methods are executed by applying filters to the full set of seismic gather data in the f-k domain in order to obtain a resulting wavefield from recorded pressure and/or particle velocity data. The output of the filter is iteratively decomposed according to local dip values using eigenimage processing based on singular value decomposition ('SVD'). The same sample locations are extracted using SVD from the input in addition to generating input for a subsequent iteration with already processed data removed. Eigenimage processing methods allow for correct treatment of spatially aliased energy in f-k domain filtering.

Systems and methods for frequency-domain filtering and space-time domain discrimination of seismic data

Variable depth multicomponent sensor streamer. At least some of example embodiments are methods including designing a depth profile for first portion of a sensor streamer by determining a first target depth for a first hydrophone-geophone pair, the first hydrophone-geophone pair at a first offset along the sensor streamer, the determining based on a first projected geophone noise floor at the first offset and a first expected spectral notch of a hydrophone of the first hydrophone-geophone pair; and determining a second target depth for a second hydrophone-geophone pair, the second hydrophone-geophone pair at a second offset along the sensor streamer, the second offset greater than the first offset, and determining the second target depth based on a second projected geophone noise floor in the sensor streamer at the second offset and a second expected spectral notch of a hydrophone of the second hydrophone-geophone pair; wherein the second target depth is greater than the first target depth.

Dual-sensor seismic data are separated into aliased and unaliased parts in a frequency-wavenumber domain. The seismic data in the unaliased part are processed using a conventional vertical wavenumber. The seismic data in the aliased part are processed using an alternative vertical wavenumber additionally based on a Nyquist wavenumber for the seismic data. The processed unaliased seismic data and the processed aliased seismic data are combined.

Method for processing dual-sensor streamer data with anti-alias protection

Recorded seismic data are represented as a convolution of operators representing a reflectivity series of the earth and a seismic wavelet. The recorded seismic wavelet is represented as a convolution of operators representing a receiver ghost, a source ghost, a ghost-free source system response, an earth filter response, and a receiver system response. The operator representing the receiver ghost is removed from the convolution representing the seismic wavelet. The operator representing the source ghost is removed from the convolution representing the seismic wavelet. The operator representing the ghost-free source response is removed from the convolution representing the seismic wavelet. The operator representing the earth filter response is removed from the convolution representing the seismic wavelet. The operator representing the seismic wavelet is removed from the convolution representing the recorded seismic data.

Method for eliminating spectral constraints of acquisition system and earth filtering effects

Filters are applied to seismic signals representative of subsurface formations to generate filtered signals with attenuated spatially aliased energy. The filtered signals are multiplied in the frequency-wavenumber domain by a complex function of frequency and wavenumber representing the seismic attribute in the frequency-wavenumber domain, to generate scaled signals. The scaled signals, transformed to the time-space domain, are divided by the filtered signals in the time-space domain, to a seismic attribute useful for identifying and characterizing the subsurface formations.

Method for calculation of seismic attributes from seismic signals

A cross-line slowness is determined for each sample in the signals in towed marine seismic streamers. A range of assumed cross-line slownesses is selected. Vertical wavenumbers are determined using the range of assumed cross-line slowness determined for samples in the signals of pressure sensors and particle motion sensors in the towed marine seismic streamers. The determined vertical wavenumbers are used to correct the particle motion sensor signals for angle of incidence along the direction of the seismic streamers and transverse thereto to generate a corrected particle motion sensor signal. The corrected particle motion sensor signals are combined based on the determined cross-line slowness for the samples. The corrected particle motion sensor signal and the pressure sensor signal are used to determine at least one of upgoing and downgoing pressure components and upgoing and downgoing particle motion components of the particle motion sensor and pressure sensor seismic signals.

Method for combining signals of pressure and particle motion sensors in marine seismic streamers

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 determining a fault in a seismic air gun includes comparing a near field seismic signal measured during operation of the air gun to a reference near field signal and determining the existence of a fault in the air gun when a difference between the measured near field signal and the reference near field signal exceeds a selected threshold.

Method for detecting air gun faults in a marine seismic source array

Seismic data sets representative of a marine seismic streamer survey are constructed with test coverage holes in the data sets. The data sets are processed and data quality degradation in the processed data due to the test coverage holes is evaluated. Maximum acceptable coverage holes for the survey are determined from the evaluation of data quality degradation.

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Drammen, Norway

Anthony James Day