Abstract: Marine surveys carried out with multiple source arrays comprising three or more sources are discussed. Each source of a multiple source array is an array of source elements, such as air guns. The sources of a multiple source array may be arranged in particular type of configuration that is effectively maintained while the survey vessel travels a sail line. The sources of the multiple source array are activated to acoustically illuminate a subterranean formation with acoustic signals. Two or more sources of a multiple source array may be activated to create blended seismic data.

Abstract: Marine surveys carried out with multiple source arrays comprising three or more sources are discussed. Each source of a multiple source array is an array of source elements, such as air guns. The sources of a multiple source array may be arranged in particular type of configuration that is effectively maintained while the survey vessel travels a sail line. The sources of the multiple source array are activated to acoustically illuminate a subterranean formation with acoustic signals. Two or more sources of a multiple source array may be activated to create blended seismic data. Methods to deblend, source deghost, and attenuate noise in the blended seismic data obtained by using a multiple source array are also discussed.

Abstract: The invention pertains to a target point detection method for an automatic search of at least one target point in a surveying environment in advance of a precise measurement of the at least one target point with a surveying device. In some embodiments, the surveying environment may include a plurality of points of non-interest, where a point of non-interest is a reflective object or surface, or a target comprising at least one retroreflector being positioned at each target point. In some embodiments, a method may include emitting electromagnetic radiation to illuminate retroreflectors emitted in the form of a vertical fan which is movable through a horizontal angular range; receiving signals reflected from retroreflectors within a fan-shaped detection area, determining at least a horizontal angle to the retroreflectors, assigning a time mark and/or a distance to each of the signals, and storing the detected signal in a two-dimensional data structure.

Abstract: A measured pressure field, a measured vertical velocity field, and two measured orthogonal horizontal velocity fields are obtained. A programmable computer is used to perform the following. A scaling factor is determined from water acoustic impedance, the measured pressure field, and the horizontal velocity fields. One of the measured pressure field and measured vertical velocity field is combined with one of the measured vertical velocity field scaled by the scaling factor and the measured pressure field scaled by the scaling factor, generating one of up-going and down-going pressure and velocity wavefields.

Abstract: A technique includes receiving a pressure measurement and a particle motion measurement from at least towed seismic sensor. The pressure measurement contains signal and noise. The technique includes estimating the signal in the pressure measurement and based at least on the estimated signal in the pressure measurement, estimating a noise in the pressure measurement. Noise in the particle motion measurement is predicted based on at least the estimated noise in the pressure measurement, and the particle motion measurement is processed to remove noise based on at least the predicted noise.

Abstract: Seismic processing method, in which, in order to eliminate multiple reflections on seismic data, seismic data are migrated in time or in depth (110) arid the data thus migrated are processed to determine an approximation of multiple reflections to be subtracted from, seismic data (120 to 160).

Abstract: The invention is a method for suppressing noise in controlled source electromagnetic survey data based on the frequency content of the noise. The invention recognizes that some data variations across bins cannot be attributed to resistivity variations within the earth. This variation across bins constitutes a model of noise in such surveys, and the invention mitigates noises that obey this model. Noise varying rapidly in either space or time is removed by filtering temporal frequency domain data (131) with a low-pass filter (134) having a selected cutoff frequency (133).

Abstract: The method for suppressing noise in the controlled seismic source electromagnetic survey data based on the frequency content of the noise (51) contained in the data. The invention recognizes that some data variations across bins cannot be attributed to resistivity variations within the earth. This variation across the bins constitutes a model of noise in such surveys, and the invention mitigates noise that obeys this model.

Abstract: A technique includes obtaining first data indicative of seismic measurements acquired by seismic sensors of a first set of towed streamers and obtaining second data indicative of seismic measurements acquired by seismic sensors of a second set of towed streamers. The second set of towed streamers is towed at a deeper depth than the first set of towed streamers. The technique includes interpolating seismic measurements based on the first and second data. The interpolation includes assigning more weight to the second data than to the first data for lower frequencies of the interpolated seismic measurements.

Abstract: Method for denoising a receiver signal from a controlled source electromagnetic survey. A discrete wavelet transform is performed on the signal, and the resulting detail coefficients are truncated using a selected threshold value, which may be zero. Further levels of decomposition may be performed on the approximation coefficients from the preceding level. After the final level of decomposition, a denoised signal is restructured by performing the inverse wavelet transformation on the last set of approximation coefficients combined with the thresholded detail coefficients accumulated from all levels of decomposition.

Abstract: A method is disclosed for processing seismic data. The method includes determining a position of a seismic energy source and seismic receivers at a time of actuation of the source. A velocity of the seismic receivers with respect to the source position is determined at the time of actuation. An offset of the receivers is corrected using the velocity. A moveout correction is determined for the signals detected by the sensors based on the corrected offset and a velocity of earth media through which seismic energy passed from the source to the sensors.

Abstract: This invention relates to improved methods to generate shaped sweeps, and for the acquisition of vibroseis data with a shaped pilot sweep.

Abstract: The invention is a method for removing trapped water bottom multiples, receiver side peg-leg multiples, and source side peg-leg multiples from dual sensor OBC data, where the data includes both pressure signals and velocity signals. The pressure and velocity signals are compared to determine any polarity reversals between them. Polarity reversals are used to identify and separate up-going and down-going wavefields in the pressure and velocity signals. A matching filter is applied to a portion of the velocity signal where polarity reversals exist. The down-going wavefield is then estimated by calculating the difference between the portion of the velocity signal where polarity reversals exist and the portion of the pressure signal where polarity reversals exist and applying a scaling factor to the result. An attenuated up-going pressure wavefield is then determined by combining the estimated down-going wavefield and the pressure signal.

Abstract: Providing a set of seismic sources in a focusing array to enable concentrating seismic energy in a selected target point (k) in an underground formation, by performing a standard seismic survey of the underground formation using a set of impulsive seismic sources and a set of downhole seismic receivers j, and recording the signals uij(t), selecting a position k to be the target point; obtaining from the signals uij(t) the one-way travel times &tgr;ik from a number of sources i to the target point at the location k; and calculating ti=t0−&tgr;ik to obtain the activating times ti at which the impulsive seismic sources i have to be activated, in order to get a focusing array of the seismic sources i of which the seismic waves arrive at the target point k in phase at time to.

Abstract: A system and method of processing seismic signals wherein seismic data resulting from a reflected seismic wave is received at a multi-component receiver. A mask trace is generated as a function of the seismic data received at the multi-component receiver, and a single type of seismic signals from the seismic data received at the multi-component receiver is identified and extracted utilizing the mask trace. Generating the mask trace further includes multiplying the seismic data received at two of the components of the multi-component receiver to produce a first result. A positive/negative sign of the first result is identified to produce a first binary result. The first binary result is divided by a scaling factor to produce the mask trace.

Abstract: The objective of this invention is to provide a method for estimating, in the frequency domain, deconvolution operators for removing spurious resonant coupling responses from the cross-line and the vertical seismic signal components in OBC surveys. The purpose is to balance the spectral response of the respective signal component in amplitude and phase in a manner consistent with the field geometry.

Abstract: A method for attenuating water column reverberations in a dual sensor seismic signal, whereby a pressure signal and a velocity signal are transformed from the time domain to the frequency domain, generating a transformed pressure signal and a transformed velocity signal, respectively. Values for weighting factors K.sub.p and K.sub.v are selected and multiplied times the transformed pressure signal and the transformed velocity signal, respectively, generating a weighted pressure signal and a weighted velocity signal, respectively. The weighted pressure signal and the weighted velocity signal are summed, generating a summed signal. Values for ocean bottom reflectivity R and Z, the frequency domain delay operator for two-way travel time in the water layer, are determined. A weighted inverse Backus filter is calculated and multiplied times the summed signal, generating a filtered signal. The filtered signal is transformed from the frequency domain to the time domain.

Abstract: A computer system and method for eliminating the effects of ghost reflections from marine seismic survey traces obtained via ocean bottom cables are disclosed. Dual sensors are used in the ocean bottom cables, to obtain both pressure and velocity traces. The disclosed method combines, in a common receiver gather, the corresponding pressure and velocity traces for each source-receiver path using several values of a scalar value that serves as a weighting factor. Conventional corrections and filtering, including spiking deconvolution, are applied to the combined traces, and the combined traces for each value of the scalar are stacked over a limited offset range. Autocorrelation and other spectral techniques may be applied to identify the residuals of the ghost reflections using each of the multiple scalar values; the optimal value may then be selected, for each common receiver gather, as that which has the minimum ghost reflection residuals.

Abstract: A method is described that attenuates reverberations in ocean bottom cable data used to generate a seismic profile. First, a seismic wave is generated and recorded by pressure and particle velocity sensor pairs. Adding the product of the pressure data times the absolute value of the velocity data and the product of the velocity data times the absolute value of the pressure data eliminates reverberations, leaving a combined signal that is a function of only the primary wave response signal. Dividing this combined signal by the number 2 and a sensitivity scaling factor, and then taking the square root of the result produces the magnitude of the primary signal. Replacing the positive/negative sign of the combined signal that existed before taking the absolute value provides the proper polarity. The data are then incorporated into a seismic profile.

Abstract: A method of processing data from a co-located hydrophone-geophone pair of seismic receivers of an ocean-bottom cable system. Ambient noise is obtained for the hydrophone and geophone. A relative noise signal is determined by finding the normalized difference between geophone and hydrophone noise signals. Geophone and hydrophone data signals are then scaled by an amount equal to the relative noise signal.

Abstract: A system for compensating for noise induced in a sensor data stream from a sensor array towed by a towing device includes a towing device motion data input receives a towed motion data stream representative of towing motion of the towing device. A sensor array input for receiving the sensor data stream. An adaptive filter connected to the towing device motion data input and the sensor array input for receiving the towed motion data stream from the towing device motion data input and the sensor data stream from the sensor array input and for generating a corrected sensor data stream representing sensor array data with ship motion noise attenuated therefrom.

Abstract: A process for the extraction of a time-variable useful signal having a finite spatial extension by an array of N sensors or transducers (N being equal to or greater than 3), that receive the useful signal to which have been added q spatially coherent additive noises (q being less than N). According to the process, unprocessed signals are acquired on the output of each sensor, filtered in order to restrict them to the frequency band of the useful signal and digitized. Then, spatial prediction error signals of the noise are calculated and analyzed so as to carry out the detection of the useful signal and its separation from the q additive noises. A device for extracting a useful signal according to the process is also disclosed.

Abstract: Seismic data from co-located sensors of different genera are formatted into common velocity-receiver gathers and common pressure receiver gathers. A first ratio between the velocity signature amplitudes and the pressure signature amplitudes is measured within a fixed analysis window. A second ratio is measured between the pressure and velocity signatures for a weighting-zone window of limited extent. The first and second ratios are combined to form an equalization operator. The pressure and velocity signatures from within the weighting zone window are combined in the presence of the equalization operator to define a transient-free time-scale datum.

Abstract: A method for simultaneous collection of seismic data of shallow and deep targets, in which two seismic streamers are towed at different water depths (1 and 2 in FIG. 2), and only one acoustic source of seismic signals is used. The seismic data recorded by the different streamers are mixed in a subsequent processing step, seismic data being weighted before being mixed by a weight which is made dependent on the recorded two-way travel time for the respective streamers, so that data from one or several streamers located at the least water depth receive a weight which decreases with travel time, whereas data from a corresponding number of streamers of greater depths receive a weight which increases with travel time.

Abstract: A method of reducing horizontally propagating pressure waves in marine seismic exploration improves the signal-to-noise ratio at associated receivers and reduces interference at unassociated receivers. Marine vibrators are arranged into an array with a given separation between each vibrator, so that horizontally propagating pressure waves from the vibrators which generally traverse the array are out-of-phase at most frequencies of vibration. The amplitude output from each vibrator varies with the output frequency of each vibrator to maximize the cancellation of out-of-phase pressure waves along the array. A receiver, which usually includes a plurality of hydrophones disposed in a streamer, is spaced from the marine vibrators at a distance sufficient to establish the receiver as being in the far-field. The output of each of the marine vibrators is locked in phase and frequency with a known pilot signal so that downwardly propagating pressure waves are substantially unaffected.

Abstract: Described is a method of driving a seismic vibrator with a control signal to produce an output signal having minimized harmonic distortion. The method includes the steps of producing a plurality a harmonic distortion signals related to a fundamental frequency of the control signal. The phase and amplitude of said harmonic distortion signal is varied to produce with the vibrator suites of variations of the distortion signal. From among suites of variations there is selected that harmonic distortion signal having phase and amplitude values which produce a minimum value in harmonic distortion signal amplitude. The steps are repeated for different fundamental frequencies and the selected signals are summed with their related fundamental frequencies to produce a vibrator sweep control signal. The seismic vibrator is driven with the control signal to produce an output in which harmonic distortion is significantly attenuated.

Abstract: Method and apparatus for digitally deriving arrays from seismic data. Indentical parallel processing elements connected between common input/output buses are each preselected to derive different pluralities of arrays. Array specifications defining the arrays are downloaded into the processing elements. A scan sample set of spatially distributed seismic receivers is periodically generated and placed on the input bus. Each processing element, in response to array specifications, captures and stores all receiver output signals in the scan required to derive its respective arrays, derives its assigned arrays, and delivers resultant array samples to the output bus. Double input and output buffering in the processing elements is provided whereby receiver capture, array derivation, and outputing processes occur simultaneously in each processing element.

Abstract: A marine seismic cable comprising a plurality of universal sections, each section including a plurality of fundamental arrays, preferably positioned end-to-end. Each of the arrays are separately wired to a logic circuit in one of the connectors or cans between sections and wiring is provided for connections to each of the fundamental arrays in at least an adjoining section. The logic circuits are controlled by control signals to produce composite responses from a selected grouping of fundamental arrays and, preferably, also to produce weighted or tapered responses by connecting and emphasizing each of the fundamental responses in the desired weighted manner.

Abstract: A logging sonde has directivity control of multiple sources and receivers in linear arrays. Each of the sources produces acoustic pulses which are delayed by a time delay between the sources to direct acoustic energy at an angle such that the resulting acoustic wave strikes a vertical formation orthogonally. The reflections of the acoustic pulses are detected with a linear array of receivers. The acoustic pulse detected by each receiver is delayed by an amount such that the total differential moveout for a reflected directional wave is zero.

Abstract: A multi-channeled digital seismic field stacking system is disclosed for obtaining the composite response to a variable source array. A variable source array is synthesized by applying preselected weighting coefficients to the seismic signals produced in response to a selected number of surface energy impulses. The seismic signals produced by these impulses are amplified, multiplexed and digitized to obtain digital samples to which are applied the weighting coefficients. A digital multiplier is used to multiply each digital sample by a weighting coefficient to obtain a weighted digital sample. Each digital sample is multiplied by two weighting coefficients, a partial and a final. The partial weighted samples from each of the impulses are summed together to form a partial stack, while the final weighted samples are summed together to form a final stack. The variable source array which is synthesized covers two station intervals.

Abstract: A novel array of vertically and horizontally spaced hydrophones is shown which is capable of high ratio of desired signal to noise because of good directional sensitivity when used with any seismic source. Alternatively, a novel directionally sensitive array of vertically and horizontally spaced seismic sources is disclosed for use in seismic surveying with any spread of hydrophones or geophones, again attaining a high ratio of desired signal to noise. A reception pattern (in the first case) and a radiation pattern (in the second place) is produced which essentially eliminates reception or radiation at all frequencies except for waves within a predetermined angle with respect to the array. The sensitivity is essentially constant within such angle for all frequencies and essentially zero outside it.

Abstract: A multi-purpose seismic transducer includes a first seismic sensor having a first transfer function. A transfer-function shaping filter is coupled to the output of the first seismic sensor. The filter is adjustable to shape the first transfer function to match a plurality of different second transfer functions.