Pgs Geophysical As

Pgs Exploration (uk) Limited

Pgs Exploration Limited

Gregory Ernest Parkes

Stian Hegna

Walter Söllner

Rune Tønnessen

Anthony James Day

Antoni Marjan Ziolkowski

Nils Lunde

Norman Daniel Whitmore, Jr

Peter Aaron

Charles Lameloise

Seismic data are acquired using a seismic source comprising a plurality of seismic sub-sources disposed in a body of water at a plurality of depths and activated with different time delays. Far-field signatures are determined for the plurality of seismic sub-sources at each of the plurality of depths. A composite ghost-free far-field signature of the seismic source is determined from the far-field signatures for the plurality of seismic sub-sources at each of the plurality of depths and different time delays. A source response is removed from the seismic data using the far-field signatures of the seismic source

Method and system for determining source signatures after source ghost removal

Seismic data are acquired by actuating a first source at a first time and one or more additional seismic sources each with their own characteristic times with respect to a time of signal recording, the sources substantially collocated and at different depths. A first wavefield is determined that would occur if the first source were actuated at a selected time with respect to an initiation time of the recordings and being time adjusted for the water depth. One or more additional wavefields are determined that would occur if the one or more additional sources were each actuated at said selected time with respect to said initiation time, and being time adjusted for water depths of the one or more additional sources. The first wavefield and the one or more additional wavefields are combined to determine a deghosted source wavefield corresponding to actuation of a single seismic energy source.

Wavefield deghosting of seismic data recorded using multiple seismic sources at different water depths

A method for marine seismic surveying includes separating up-going and down-going wavefields from seismic energy emitted by at least one marine seismic energy source. The separated up-going and down-going wavefields are propagated from the at least one marine seismic energy source to at least one of a water surface and a common reference depth. One of the up-going and down-going wavefields is phase shifted 180 degrees. The propagated, phase shifted up-going and down-going wavefields are summed.

Method for acquiring and processing marine seismic data to extract and constructively use the up-going and down-going wave-fields emitted by the source

Seismic data are acquired using a seismic source comprising a plurality of seismic sub-sources disposed in a body of water at a plurality of depths and activated with different time delays. Far-field signatures are determined for the plurality of seismic sub-sources at each of the plurality of depths. A composite ghost-free far-field signature of the seismic source is determined from the far-field signatures for the plurality of seismic sub-sources at each of the plurality of depths and different time delays. A source response is removed from the seismic data using the far-field signatures of the seismic source.

A method for acquisition and processing of marine seismic signals to extract up-going and down- going wave-fields from a seismic energy source includes deploying at least two marine seismic energy sources at different depths in a body of water. These seismic energy sources are actuated with known time delays that are varied from shot record to shot record. Seismic signals from sources deployed at different depths are recorded simultaneously, Seismic energy corresponding to each of the sources is extracted from the recorded seismic signals. Up-going and down-going wave-fields are extracted from the sources deployed at different depths using the extracted seismic energy therefrom. A method includes the separated up-going and down-going wave-fields are propagated to a water surface or a common reference, the up-going or the down-going wave-field is 180 degree phase shifted, and the signals from these modified up-going and down-going wave-fields are summed.

Method for acquiring and processing marine seismic data to extract and constructively use the up-going and down-going wave-fields emitted by the source(s)

A disclosed subsurface imaging method begins by obtaining initial signals from a geophysical survey that has been acquired with multiple geophysical energy sources actuated in a plurality of firing sequences, each sequence having a known time delay between the firing times of each source. The initial signals are grouped into gathers of signals acquired from multiple firing sequences. For each gather, initial estimates of the first and second source wave fields are determined. Quieted signals for the first source are then generated to represent the initial signals minus a current estimate of the second source wave field. A coherent energy separation operation is applied to the quieted signals to obtain a refined estimate for the first source wave field.

Subsurface imaging systems and methods with multi-source survey component segregation and redetermination

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

A disclosed seismic source assembly includes a body having a cavity and a seismic source positioned in the cavity. The cavity is in fluid communication with the water via an aperture oriented in a first direction. One or more surfaces of the body define a water contact significantly larger than an area of the aperture and on a side opposite the first direction. A described method includes forming a source assembly by: providing a cavity having an aperture for transmitting seismic waves; rigidly attaching a base to a side of the cavity opposite the aperture, where a transverse area of the base is significantly larger than an area of the aperture; and positioning a seismic source in the cavity. The source assembly is submerged in the water and triggered.

Systems and methods for producing directed seismic waves in water

A method for seismic exploration of subsurface rock formations includes actuating an impulsive seismic energy source proximate the rock formations. A non-impulsive seismic energy source is actuated. A near field waveform of each of the impulsive and non-impulsive seismic energy sources is detected. A far field waveform of the combined output of the impulsive and non-impulsive seismic energy sources is determined from the near field waveforms. An impulse response of the subsurface rock formations is determined by deconvolving the far field waveform with detected seismic signals.

Combined impulsive and non-impulsive seismic sources

A method for acquisition and processing of marine seismic signals to extract up-going and down-going wave-fields from a seismic energy source includes deploying at least two marine seismic energy sources at different depths in a body of water. These seismic energy sources are actuated with known time delays that are varied from shot record to shot record. Seismic signals from sources deployed at different depths are recorded simultaneously. Seismic energy corresponding to each of the sources is extracted from the recorded seismic signals. Up-going and down-going wave-fields are extracted from the sources deployed at different depths using the extracted seismic energy therefrom. A method includes the separated up-going and down-going wave-fields are propagated to a water surface or a common reference, the up-going or the down-going wave-field is 180 degree phase shifted, and the signals from these modified up-going and down-going wave-fields are summed.

Method for aquiring and processing marine seismic data to extract and constructively use the up-going and down-going wave-fields emitted by the source(s)

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

Physical parameters are measured for an array of seismic sources, preferably for each activation of the seismic sources. Calibration functions are obtained and the measured physical parameters and calibration functions are applied to a model, which generates a calibrated source signature for the array of seismic sources. Alternatively, the measured physical parameters are applied to a model, which generates a modeled source signature, and then the calibration functions are applied to the modeled source signature to generate the calibrated source signature. Alternatively, modeled source signatures are generated for each seismic source and then the calibration functions are applied to the modeled source signatures to generate a calibrated source signature for each seismic source. Then the calibrated source signatures for each seismic source are combined, preferably by linear superposition, to generate the calibrated source signature for the array of seismic sources.

Growing community of inventors

Corsham, United Kingdom

Gregory Ernest Parkes