It is proposed a positioning assistance system for a vibrator truck, that is configured to determine a vibration point distance between the vibrator truck and the vibration point location; determine a stopping distance for stopping the vibrator truck at a vibration point location, according to a determined current speed of the vibrator truck and according to a speed profile; determine a time for stopping the vibrator truck at the vibration point location according to the current speed of the vibrator truck, when the stopping distance corresponds to said vibration point distance; and trigger the lifting down of the baseplate of the vibratory system, when at least the following condition is met: said stopping time is inferior or equal to a time for lifting down the vibratory system to the ground. Corresponding vibrator truck and method are also proposed.

Methods and systems to separate seismic data associated with impulsive and non-impulsive sources are described. The impulsive and non-impulsive sources may be towed through a body of water by separate survey vessels. Receivers of one or more streamers towed through the body of water above a subterranean formation generate seismic data that represents a reflected wavefield produced by the subterranean formation in response to separate source wavefields generated by simultaneous activation of the impulsive source and the non-impulsive source. Methods and systems include separating the seismic data into impulsive source seismic data associated with the impulsive source and non-impulsive source seismic data associated with the non-impulsive.

Disclosed are acoustic logging systems and methods that involve correlating broadband acoustic signals acquired by a plurality of acoustic sensors at multiple depths within a wellbore to compute covariance matrices and their eigenvalues in the frequency domain for a plurality of frequency bins. In accordance with various embodiments, acoustic sources are detected and located based on the eigenvalues viewed as a function of depth and frequency.

A method is provided of inspecting a nested multi-layer structure including a first and second electrically conductive layer and a third layer disposed behind the second conductive layer. The method includes deploying a sensor device including an electromagnetic acoustic transducer to a borehole location proximate to the structure, generating a drive signal including a plurality of frequencies, applying an electrical current signal to the sensor device based on the drive signal and inducing currents in the first conductive layer that induce currents generating acoustic signals having the plurality of frequencies, detecting a first set of resonant frequencies based on received electromagnetic signals, detecting a second set of resonant frequencies based on received acoustic signals, estimating a property of the first and/or the second conductive layer based on the first set of resonant frequencies, and estimating a property of the third layer based on the second set of resonant frequencies.

A method is provided of inspecting a nested multi-layer structure including a first and second electrically conductive layer and a third layer disposed behind the second conductive layer. The method includes deploying a sensor device including an electromagnetic acoustic transducer to a borehole location proximate to the structure, generating a drive signal including a plurality of frequencies, applying an electrical current signal to the sensor device based on the drive signal and inducing currents in the first conductive layer that induce currents generating acoustic signals having the plurality of frequencies, detecting a first set of resonant frequencies based on received electromagnetic signals, detecting a second set of resonant frequencies based on received acoustic signals, estimating a property of the first and/or the second conductive layer based on the first set of resonant frequencies, and estimating a property of the third layer based on the second set of resonant frequencies.

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.

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.

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.

A modular downhole logging system includes a transmitter module having a local frequency, wherein the transmitter module transmits interrogation signals into a formation based on the local frequency. The downhole system also includes a receiver module axially-spaced from the transmitter module and that receives response signals corresponding to the interrogation signals, wherein the receiver module includes sampling logic and sync estimation logic. The sync estimation logic is configured to perform sync estimation operations including estimating the local frequency of the transmitter module based on analysis of response signal Fourier transform results corresponding to different frequencies. The sampling logic/clock is configured to sample the response signals based on the estimated local frequency of the transmitter module, wherein a processor derives formation property values using the sampled response signals.

Improved methods of providing acoustic source signals for seismic surveying, wherein a plurality of signals can be easily separated from one another after data acquisition, wherein the source signals are not sweep based.