Abstract: Noise can be attenuated in marine seismic data from a marine seismic survey. A first near-continuous measurement of a wavefield and a second near-continuous measurement of the wavefield recorded from a marine seismic survey can be equalized, a coherent portion of the equalized second near-continuous measurement can be collapsed, and a noise model can be derived. The noise model can be subtracted from the second near-continuous measurement.

Abstract: An inline source can be used for a marine survey. For example, a marine survey vessel can tow source units in line. The source units can be actuated near-continuously to cause a respective signal emitted by each of the source units to be uncorrelated with signals emitted by other of the source units.

Abstract: Methods and apparatus are described for using ambient acoustic energy as a passive source in marine seismic surveys. An example embodiment includes (a) accessing signals that were recorded by sensors in the presence of acoustic energy that was emitted by a passive source during a marine seismic survey; (b) identifying a point to represent a location from which the acoustic energy was emitted; (c) isolating, from the recorded signals, a direct wavefield arriving at the sensors from a direction of the identified point; and (d) generating an estimated passive source wavefield at the identified point by backpropagating the isolated direct wavefield to the identified point. The estimated passive source wavefield may be used, together with signals recorded by the sensors, to generate an image of a subsurface earth volume without the use of active seismic sources.

Abstract: Techniques are disclosed relating to performing marine surveys with non-uniform spacing of survey elements in a cross-line direction. This may include, for example, performing a survey pass in a multi-pass survey by towing a plurality of sources and sensors in a towing pattern with non-uniform spacing between adjacent ones of the sources. In some embodiments, the non-uniform spacing between adjacent ones of the sources is determined based on a common mid-point (CMP) spacing parameter for the survey pass in the cross-line direction. The spacing parameter may relate, for example, to difference in average CMP spacing for different parts of the survey spread, variance in CMP spacing, and/or width of the survey spread for which a threshold CMP spacing distance is satisfied. In various embodiments, the disclosed techniques may improve survey resolution and/or accuracy and may require a smaller number of survey passes and/or a reduced amount of survey equipment relative to traditional techniques.

Abstract: Methods and apparatus are described for reducing noise in measurements made by one or more pressure sensors disposed in a cable having a generally longitudinal axis. Estimated axial vibration noise at a location along the cable is determined based at least in part on measurements from one or more motion sensors disposed along the cable. The estimated axial vibration noise is subtracted from pressure sensor measurements corresponding to the location. The result is noise-attenuated pressure sensor measurements corresponding to the location.

Abstract: Estimating an earth response can include deconvolving a multi-dimensional source wavefield from near-continuously recorded seismic data recorded at a receiver position. The deconvolving can include spreading the near-continuously recorded seismic data across a plurality of possible source emission angles. The result of the deconvolution can be the earth response estimate.

Abstract: A method for seismic data processing can include obtaining seismic data acquired based upon trigger times and not based upon positions of triggered source elements. The seismic data can include near-continuously recorded seismic data in split records. The split records can be spliced together into a single near-continuous record to produce a trace with seismic data from a single acquired line. The seismic data can be processed by performing a spatial shift for each of a number of time samples to correct for motion of a number of seismic receivers.

Abstract: Techniques are disclosed relating to geophysical surveying and data processing using streamers at different depths. In one embodiment, a method includes obtaining geophysical data specific to a geophysical formation that includes a first set of data representative of a first particle motion signal and a first pressure signal recorded using sensors at a first depth and a second set of data representative of a second particle motion signal and a second pressure signal recorded using sensors at a second, greater depth. In this embodiment, the method includes generating first and second wave separation equations from the first and second sets of data and determining a cross-line wavenumber value that reconciles the first and second equations. The determined cross-line wavenumber may be used to separate measured up-going and down-going wavefields.

Abstract: 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.

Abstract: 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.

Abstract: Processes and systems described herein are directed to performing marine surveys with a moving vibrational source that emits a continuous source wavefield into a body of water above a subterranean formation. The continuous source wavefield is formed from multiple sweeps in which each sweep is emitted from the moving vibrational source into the body of water with a randomized phase and/or with a randomized sweep duration. Reflections from the subterranean formation are continuously recorded in seismic data as the moving vibrational source travels above the subterranean formation. Processes and systems include iteratively deconvolving the source wavefield from the continuously recorded seismic data to obtain an earth response in the common receiver domain with little to no harmful effects from spatial aliasing and residual crosstalk noise. The earth response may be processed to generate an image of the subterranean formation.

Abstract: Processes and systems for imaging a subterranean formation using continuously recorded seismic data obtained during a marine seismic geophysical survey of the subterranean formation are described herein. The processes and systems compute upgoing pressure data at stationary-receiver locations. and low-frequency noise attenuation processes and systems are applied to the upgoing pressure wavefield data to obtain low-frequency noise attenuated upgoing pressure wavefield data. An image of the subterranean formation, or data indicative thereof, may be generated using the low-frequency noise attenuated upgoing pressure wavefield data at stationary-receiver locations.

Abstract: An inline source can be used for a marine survey. For example, a marine survey vessel can tow source units in line. The source units can be actuated near-continuously to cause a respective signal emitted by each of the source units to be uncorrelated with signals emitted by other of the source units.

Abstract: Source element of a source subarray can be individually actuated according to an actuation sequence. The actuation sequence can be at least partially based on a relative position of each of the source elements within a particular geometry of the source subarray with respect to a previously actuated source element and a towing velocity of the source subarray.

Abstract: A first portion of electric potentials generated by a first detector and a second detector of a hydrophone can be isolated, wherein the first portion is indicative of particle motion. A second portion of the electric potentials generated by the first detector and the second detector of the hydrophone can be isolated, wherein the second portion is indicative of pressure.

Abstract: Alternating current (AC) coupled accelerometer calibration can include acquiring calibrated data from a direct current (DC) coupled accelerometer of a towed object and interpolating the acquired calibrated data to a location of an AC coupled accelerometer of the towed object. AC coupled accelerometer calibration can also include estimating a calibration parameter associated with the AC coupled accelerometer based on the interpolating and correcting for a sensitivity associated with the AC coupled accelerometer using the calibration parameter.

Abstract: A method and apparatus for determining marine seismic source configurations which produce a minimum error after the process of combining the wave fields to eliminate the responses of sources including the source ghost operated at multiple depths, without separating these wave fields, is disclosed. In one embodiment, a method includes simulating, on a computer system, the performing of a seismic survey for one or more source configurations. An error term is calculated for each configuration simulated. Based on the calculated error terms, a configuration having the smallest error among those simulated may be determined.

Abstract: Source element of a source subarray can be individually actuated according to an actuation sequence. The actuation sequence can be at least partially based on a relative position of each of the source elements within a particular geometry of the source subarray with respect to a previously actuated source element and a towing velocity of the source subarray.

Abstract: Techniques are disclosed relating to geophysical surveying and data processing using streamers at different depths. In one embodiment, a method includes obtaining geophysical data that is specific to a geophysical formation and representative of: a particle motion signal recorded using sensors at a first depth, a first pressure signal recorded using sensors towed at the first depth, and a second pressure signal recorded using sensors towed at a second, greater depth. In this embodiment the method includes modifying a low-frequency range of the particle motion signal using particle motion information estimated based on the second pressure signal. The modified particle motion signal may then be used to separate up-going and down-going wavefields. In some embodiments, obtaining geophysical data is performed by towing a first streamer at the first depth and a second streamer at the second depth. In some embodiments, the second streamer does not include particle motion sensors.

Abstract: Noise can be attenuated in marine seismic data from a marine seismic survey. A first near-continuous measurement of a wavefield and a second near-continuous measurement of the wavefield recorded from a marine seismic survey can be equalized, a coherent portion of the equalized second near-continuous measurement can be collapsed, and a noise model can be derived. The noise model can be subtracted from the second near-continuous measurement.