Abstract: A method of performing normal moveout (NMO) correction and stacking of a common-midpoint (CMP) gather of seismic traces in a manner that avoids NMO stretch is disclosed. A CMP gather without NMO correction is modeled as the sum of a series of short overlapping time intervals whose center times follow the NMO curve as it changes with offset. The sample values contained in these intervals are solved simultaneously by performing a statistical fit to the CMP gather based on this model. A CMP stacked trace is formed by summing these intervals at their zero-offset positions at each time sample.

Abstract: Seismic detection apparatus comprising seismic detection means capable of detecting a plurality of seismic components over a defined tetrahedral volume is provided. The seismic detection means comprises four three-component geophones. Seismic data acquired by the geophones is processed to separate P-wave components from S-wave components. The geophones are spaced apart by distances smaller than the wavelength of the detected seismic components. The apparatus may be used on surface or in a marine environment or transition zone. A method of processing seismic data is also provided comprising acquiring seismic data relating to a wavefield over a selected volume of acquisition, and measuring the curl and divergence of the wavefield from the seismic data, to thereby identify seismic components within the seismic data. Additionally, an apparatus and method for hydrocarbon exploration is disclosed for using three or more seismic receivers placed in a plane and spaced closely to each other.

Abstract: A method of calculating a throw volume corresponding to a seismic data volume. A range of time shifts and a search direction for the seismic data volume are selected. A data location separation and a vertical time window are also selected. A cross-correlation is calculated between data values corresponding to first and second data locations separated by the data location separation and symmetrically located in the search direction on each side of a target data location. The cross-correlation is calculated throughout the vertical time window for each time shift in the range of time shifts. The time shift corresponding to the maximum calculated cross-correlation is stored in the throw volume.

Abstract: In one embodiment, a computer-implemented common azimuth migration seismic data processing method comprises: providing a common-azimuth input data set for a geophysical data processing volume of interest; providing a velocity model for the volume; applying an offset antialiasing operator to the input data set; and performing a recursive downward-continuation of the common-azimuth input data set to a plurality of successive common-azimuth surfaces to generate an image of the volume of interest. In one embodiment, the present invention further provides for selecting a depth dependence of an offset range employed in the downward continuation; selecting a frequency-dependence of a depth step size employed in the downward continuation; selecting a frequency dependence of a cutoff depth employed in the downward continuation; and adding reciprocal traces to the data around zero offset, for reducing imaging artifacts introduced by data edge effects.

Abstract: A method of processing seismic data, said seismic data having been obtained by: performing a plurality of sweeps, wherein each sweep comprises generating seismic signals in the earth using a plurality of vibrators by applying a pilot sweep wave-form to each vibrator, each pilot sweep being a waveform of changing frequency; measuring the force applied to the earth by each vibrator to determine a measured force waveform; and measuring the seismic signals at one or more locations remote from the vibrators; said method comprising: filtering the measured force waveform to remove harmonics of the pilot sweep and thus determining a filtered force waveform; generating an inversion operator from the filtered force waveform for each vibrator; and applying said inversion operator to the measured seismic signals to determine the contribution of each vibrator to the seismic signals.

Abstract: A method for assessing the suitability of seismic data for quantitative amplitude analysis, where the concern is excessive residual normal moveout (RNMO). The invention uses a near offset stack and a far offset stack, the time difference between the two, a mute pattern, a reflection shape assumption for the RNMO, and a waveform and frequency for the far stack traces to generate a formula that estimates far stack amplitude error caused by RNMO. The formula can be used to compensate the far stack amplitude where the error is not so great as to require reprocessing of the data. The method can also be applied to interpreted amplitude maps.

Abstract: Near-offset and far-offset seismic data volumes are time-aligned by first selecting a plurality of time shifts. The near-offset and far-offset seismic data volumes are cross-correlated at the plurality of time shifts. An initial time-shift volume and a maximum correlation volume are created from the maximal cross-correlations at the plurality of time shifts. Areas of high time shift from the initial time-shift volume and areas of low cross-correlation from the maximum correlation volume are determined. The determined areas of high time shift and low cross-correlation are filtered from the initial time-shift volume, generating a filtered time-shift volume. The filtered time-shift volume is applied to the far-offset seismic volume to generate a time-aligned far-offset volume.

Abstract: The method of the present invention provides for processing seismic data over a subsurface area of interest. Downgoing seismic data, which may be VSP data, and surface seismic data are acquired over a subsurface area of interest. An inverse operator is determined from changes in signal characteristics, which may be first-arrival signals, between consecutive depth levels of the downgoing VSP data. The inverse operator is assigned to at least one surface seismic data level. Data levels may be in time or depth. Inverse operators may be interpolated for time or depth level operators for data samples between already determined operators. Inverse operators are applied to seismic data to restore attenuated signal components.

Abstract: A method and apparatus for determining formation slowness around a borehole are provided. The Fresnel volume concept is applied for traveltime tomography. The Fresnel volume represents a sonic wave propagation path about the borehole. The application of Fresnel volume to sonic data provides for a stable inversion and makes practical 3-D tomography. Inversion is accomplished by an iterative back-projection method.

Abstract: A method and apparatus for determining isolating and/or removing a signal of interest from acoustic data. The method and apparatus may be used to measure formation slowness in a cased borehole, in which case the signal of interest may be a casing arrival signal. The casing arrival signal may be detected, rebuilt and removed from a set of acoustic data. Semblance processing is applied to the acoustic data with the casing signal removed, yielding a coherent formation slowness log. A filter band may be defined and automatically administered to detect and remove the signal of interest such as the casing signal.

Abstract: The invention relates generally to the field of quantitative sedimentologic and stratigraphic prediction. Specifically, geological data observed or inferred from core samples, cuttings, geophysical well logs and seismic data from locations within a sedimentary basin, in conjunction with a stratigraphic forward model and an inverse optimization technique, are used to predict sedimentologic and stratigraphic attributes at locations within the basin other than those at which data were collected. The model's output consists of a three-dimensional model of the sedimentologic and stratigraphic attributes for the specified basin volume.

Abstract: A method is disclosed for attenuating noise from marine seismic signals caused by a noise in the water. The method includes determining an arrival time of a noise event at each of a plurality of seismic sensors, estimating a position of the noise source from the arrival times, and attenuating the noise event from the signals detected by the seismic sensors.

Abstract: A method of seismic imaging a subsurface formation using an array of seismic sources and an array of seismic receivers located subsurface, wherein there is a complex transmission medium between the two sets by creating a virtual source at a selected receiver within the array, time-reversing a portion of the signal related to the selected source and receiver and convolving the time-reversed portion of the signal with the signal at adjoining receivers within the array and repeating the process for signals attributable to various surface sources to create a seismic image of a target formation.

Abstract: A wavelet-based method for analysis of singularities improves analysis and information gathering from seismic trace data. A wavelet transform is applied to seismic trace data. The Hölder exponent is calculated for every time point of the wavelet transform for each seismic trace. Hölder exponents are then plotted versus time. These graphs are utilized in place of seismic traces themselves in creating two and three dimensional images. The graphs produced using Hölder exponents greatly improve interpretation of stratigraphic boundaries and other geological information to be readily identified. This provides for better, more accurate stratigraphic analysis. In addition, the nature of the Hölder exponents of the seismic trace are consistent with Hölder exponents calculated from acoustic impedance of the various strata.

Abstract: A system for measuring density of material which can be embodied to measuring bulk density of material penetrated by a borehole. The probe component of the system comprises a source of neutron radiation and preferably two gamma ray spectrometers. The neutron source induces gamma radiation with energies up to about 10 MeV within the material being measured. Formation bulk density is determined by combining spectra of the induced gamma radiation with preferably two gamma ray spectrometers at differing axial spacings from the source. The high energy and dispersed nature of the induced gamma radiation yields greater radial depth of investigation than that obtainable with prior art backscatter density systems, which typically use gamma ray sources local to a probe and of energy about 1.3 MeV or less. The system can alternately be embodied to measure other material properties and to measure density of materials not penetrated by a borehole.

Abstract: The invention is a method for attenuating noise in seismic data traces, in which at least a portion of the noise is noncoherent in the common-shot domain but coherent in the common-receiver domain, the coherent noise having a move-out velocity different from the move-out velocity of the data signal in the seismic data traces. The method comprises sorting the seismic data traces into common-receiver order and using the difference in move-out velocities to separate the coherent noise from the data seismic signal. This method is useful in suppressing noise in two and four-component ocean bottom cable data.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The seismic data is transformed from the offset-time domain to the time-slowness domain using a limited Radon transformation. That is, the Radon transformation is applied within defined slowness limits pmin and pmax, where pmin is a predetermined minimum slowness and pmax is a predetermined maximum slowness. A corrective filter is then applied to enhance the primary reflection signal content of the data and to eliminate unwanted noise events. After filtering, the enhanced signal content is inverse transformed from the time-slowness domain back to the offset-time domain using an inverse Radon transformation.

Abstract: A method of combining directional seismic attributes using a supervised learning approach which may include extracting seismic information from acquired data in a direction along the spatial direction of a body of interest. The method is applicable both to onshore and offshore exploration and provides a more reliable means of detecting, separating and identifying geological features, for example gas chimneys, faults, layers, and any other type of geological objects with a spatial direction and shape. The method is also suited for the detection of reservoir changes by the use of time lapse seismic techniques.

Abstract: A hydrophone assembly is provided that has a frequency response that matches that of an accelerometer. In a preferred implementation, the frequency response resembles that of a differentiator in combination with a pair of simple lags.

Abstract: A method for generating a model of a portion of the floor of a body of water from a plurality of depth measurement sources includes determining an overlap of any of the plurality of depth measurement sources with another depth measurement source and generating a relative shift between any two depth measurement sources that overlap. For each depth measurement source that overlaps with at least one other source, generating an overall shift based on the generated relative shifts. The method also includes generating a desired grid having a plurality of grid nodes and generating a model depth at a plurality of the grid nodes based, at least in part, on a global shift for the measurements of the plurality of sources based on the relative shift. Further, an output is generated of all model depths at respective grid nodes.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The seismic data is transformed from the offset-time domain to the time-slowness domain using a Radon transformation. A high-low, preferably a time variant, high low corrective filter is then applied to enhance the primary reflection signal content of the data and to eliminate unwanted noise events.

Abstract: A method and apparatus for characterizing frequency response of a device under test (DUT) is disclosed. A repeated base bit pattern is received, the base bit pattern including a first transition from a 0-bit to a 1-bit. Then, using bit error rate distribution, multivalue voltage along the first transition is determined. Finally, the multivalued voltages are converted into frequency domain using fast Fourier transform. The apparatus includes a processor and storage with instructions for the processor to perform these operations. Using the present inventive technique, the frequency response of the DUT can be determined using an error performance analyzer such as a BERT.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The seismic data is transformed from the offset-time domain to the time-slowness domain using a high resolution Radon transformation.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The seismic data is transformed from the offset-time domain to the time-slowness domain using a Radon transformation. A high-low, preferably a time variant, high low corrective filter is then applied to enhance the primary reflection signal content of the data and to eliminate unwanted noise events.

Abstract: Seismic prospecting method and device using simultaneous emission of seismic signals obtained by coding a signal by pseudo-random sequences, and notably a periodic signal phase modulated by such sequences. Signals such as, for example, periodic signals phase modulated according to a pseudo-random code (binary for example), produced by a control unit, are for example emitted in the ground by means of vibrators, the seismic signals reflected by the subsoil discontinuities in response to the periodic signals emitted are picked up by receivers coupled with the formation and recorded in an acquisition and recording system. The periodic signals are emitted simultaneously by the vibrators.

Abstract: A method is disclosed for marine seismic surveying in which upgoing and downgoing components of a seismic wavefield at a seafloor location, and the seismic wavefield at a seismic streamer location substantially above the seafloor location are determined. The upgoing and downgoing seafloor components and the streamer seismic wavefield are used to determine a separation operator. The separation operator when applied to the streamer seismic wavefield provides an estimate of at least one of an upgoing wavefield component and a downgoing wavefield component of the determined seismic wavefield for the streamer location.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The seismic data is transformed from the offset-time domain to the time-slowness domain using a limited Radon transformation. That is, the Radon transformation is applied within defined slowness limits pmin and pmax, where pmin is a predetermined minimum slowness and pmax is a predetermined maximum slowness. A corrective filter is then applied to enhance the primary reflection signal content of the data and to eliminate unwanted noise events. After filtering, the enhanced signal content is inverse transformed from the time-slowness domain back to the offset-time domain using an inverse Radon transformation.

Abstract: A model seismic image of a subsurface seismic reflector is constructed, wherein a set of source and receiver pairs is located, and a subsurface velocity function is determined. Specular reflection points are determined on the subsurface seismic reflector for each of the source and receiver pairs. A Fresnel zone is determined on the subsurface seismic reflector for each of the specular reflection points, using the subsurface velocity function. One or more seismic wavelets are selected and a set of image points is defined containing the subsurface seismic reflector. A synthetic seismic amplitude is determined for each of the image points by summing the Fresnel zone synthetic seismic amplitude for all of the Fresnel zones that contain the image point, using the seismic wavelets. The model seismic image of the subsurface seismic reflector is constructed, using the synthetic seismic amplitudes at the image points.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. An offset weighting factor xn is applied to the amplitude data, wherein 0<n<1, and the offset weighted data is transformed from the offset-time domain to the time-slowness domain using a Radon transformation. A corrective filter is then applied to enhance the primary reflection signal content of the data and to eliminate unwanted noise events. After filtering, the enhanced signal content is inverse transformed from the time-slowness domain back to the offset-time domain using an inverse Radon transformation, and an inverse of the offset weighting factor pn is applied to the inverse transformed data, wherein 0<n<1.

Abstract: A method of migrating seismic data is provided. The seismic data has associated therewith a wavefield at a first level. The method comprises extrapolating the wavefield from the first level to a second level; correcting the extrapolated wavefield; computing intermediate sample points for an output image between the first and the second levels; computing a contribution to the wavefield at each intermediate sample point; and summing the contributions to the wavefield at each intermediate sample point.

Abstract: A method and system for performing a marine seismic survey is described, including towing at least one seismic streamer comprising a plurality of hydrophones distributed at average intervals of not more than 625 cm therealong in the water over the area to be surveyed; directing acoustic signals down through the water and into the earth beneath; receiving with the hydrophones seismic signals reflected from strata in the earth beneath the water; digitizing the output of each hydrophone separately; and filtering the output to reduce the noise present in the output and to generate a signal with a reduced noise content wherein the filtering process uses as further input the digitized output of at least one nearby hydrophone. The filtering is applied to single sensor recording prior to group-forming and thus able to detect and reduce coherent noise with a coherency length of 20 meters or less. It reduces noise such as streamer or bulge noise.

Abstract: A product-sum operation portion for performing a product-sum operation (wavelet transformation) with respect to an input time-series signal by using as a base of integral a complex function in which the imaginary number portion is &pgr;/2 shifted in phase from the real number portion, a phase calculation portion for calculating a phase &thgr; from the ratio between the real number portion and the imaginary number portion of a result of the product-sum operation, a peak time detection portion for detecting a time point at which the calculated phase &thgr; changes from 2&pgr; to zero, as a peak time, are provided. Since the wavelet transformation is performed by using a basic wavelet function that is localized in terms of time and frequency, a peak time can be promptly detected. Furthermore, since a differential operation is not employed but the product-sum operation is performed, false detection caused by noises or the like can be prevented.

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: A method for analyzing and classifying the morphology of seismic objects extracted from a 3D seismic data volume. Any technique may be used to extract the seismic objects from the 3D seismic data volume. According to the inventive method, one or more morphologic parameters are selected for use in classifying the morphology of the selected seismic objects. Geometric analyses are then performed on each seismic object to determine geometric statistics corresponding to the selected morphologic parameters. The results of these geometric analyses are used to classify the morphology of the seismic objects according to the selected morphologic parameters.

Abstract: A method of attenuating noise in three dimensional seismic data using a projection algorithm is disclosed. A frequency—space—space (“f-xy”) projection algorithm is used which is a generalization of the f-x projection algorithm. The predictability of the seismic signals in the f-xy domain constitutes the basis of the algorithm. Specifically it is demonstrated that if the seismic events are planar in the t-xy domain, then in the f-xy domain they consist of predictable signals in the xy-plane for each frequency f. A crucial step of the 2-D spectral factorization is achieved through the helical coordinate transformation. In addition to the disclosed general algorithm for arbitrary coherent noise, a specialized algorithm for random noise is disclosed. It has been found that the disclosed projection algorithm is effective even in extreme cases of poor signal to noise ratio. The algorithm is also signal preserving when the predictability assumptions hold.

Abstract: A method of generating a noise estimate during seismic surveying, including measuring noise energy having a plurality of frequencies in a second time interval. The second time interval having a second start time delayed from a first start time of a first time interval during which a first plurality of reflected seismic signals are present. The plurality of reflected seismic signals having the plurality of frequencies. The second time interval approximately concurrent with the first time interval to measure one of the plurality of frequencies of the noise energy different than one of the plurality of frequencies of the first plurality of reflected seismic signals that are present. A noise estimate is generated based on the noise energy measured.

Abstract: A method for determining from measured reflection data on a plurality of trace positions, a plurality of subsurface parameters. The method includes the steps of: preprocessing the measured reflection data into a plurality of partial or full stacks; specifying one or more initial subsurface parameters defining an initial subsurface model; specifying a wavelet or wavelet field for each of the partial or full stacks of the measured reflection data; calculating synthetic reflection data based on the specified wavelets and the initial subsurface parameters; optimizing an objective function, including the weighted difference between measured reflection data and synthetic reflection data for a plurality of trace positions simultaneously; and outputting the optimized subsurface parameters. A device for implementing this method is also included.

Abstract: A method of processing data that uses an angle dependent filter from two-component sensor data allows for attenuation of free surface multiples. Typically, the sensors that are used to produce two-component ocean bottom sensor data are hydrophones and geophones. The method decomposes the recorded dual sensor data into upgoing and downgoing wavefields by combining the recorded pressure at the hydrophone with the vertical particle velocity from the geophone recorded at the ocean floor. Surface multiple attenuation is accomplished by application of an incident angle dependent deconvolution of the downgoing wavefield from the upgoing wavefield. The method uses an angle dependent filter to calibrate the geophone response so that the different coupling of the two instruments and associated noise are taken into account. In a further embodiment, a method of attenuation of multiple reflections in seismic data is provided. The seismic data comprises pressure data and particle velocity data.

Abstract: The invention relates to a method for processing a seismic 2-D or 3-D measurement data set comprised of a multitude of seismic traces each comprising a series of data points provided with amplitude values. The inventive method is characterized by the following steps: Converting the measurement data set into a binary data set in which either the number “0” is assigned to each data point when an amplitude value is less than a predetermined threshold value, or else the number “1” is assigned to each data point; including a vicinity which is located around each binarized data point and which is defined by a predetermined cell size in a similarity analysis, hereby a value is assigned to each data point.

Abstract: A method relating to filtering coherent noise and interference from seismic data by constrained adaptive beamforming is described using a constraint design methodology which allows the imposition of an arbitrary predesigned quiescent response on the beamformer. The method also makes sure that the beamformer response in selected regions of the frequency-wavenumber space is entirely controlled by this quiescent response, hence ensuring signal preservation and robustness to perturbations. Built-in regularization brings an additional degree of robustness. Seismic signals with arbitrary spectral content in the frequency-wavenumber domain are preserved, while coherent noise and interference that is temporally and spatially nonstationary is adaptively filtered. The approach is applicable to attenuation of all types of coherent noise in seismic data including swell-noise, bulge-wave noise, ground-roll, air wave, seismic vessel and rig interference, etc. It is applicable to both linear or areal arrays.

Abstract: A method of processing seismic traces corresponding to two modes of propagation in the subsoil, the method being characterized by the following steps: determining at least one pair of correlated events from the seismic traces corresponding to the two modes respectively; determining the ratio of the differences between the vertical travel times Ts and Tp in the S domain and in the P domain, corresponding to said correlated pairs of events; and determining the values of Ts and Tp over the time interval defined by the two pairs of correlated events so that throughout said time interval, the ratio rt=Ts/Tp is equal to the ratio Vp/Vs of the speeds in the P domain and in the S domain, and so that the mean value of said ratio r over said time interval corresponds to the ratio of the differences between the vertical travel times corresponding to the pairs of correlated events.

Abstract: A method for correcting seismic data for periodic distortion introduced by acquisition parameters by filtering modified unitary transform data. A vertical transform is applied to seismic data to obtain frequency-space seismic data. These data are decomposed into an amplitude component and a phase response component. The phase response component is saved for the inverse process. A horizontal transform is applied to the amplitude component of the F-X data to obtain modified transform data. Because this transformation is performed in the X direction, it is here also referred to as the horizontal forward Fourier transformation. A K filter based on the period of the energy to be suppressed or eliminated is applied to this F-K data. The K filter may be, for example, a notch filter or any suitable filter. The data are then inverted to obtain T-X data with distortion suppressed or eliminate.

Abstract: The present invention comprises a non-iterative method of processing seismic traces. A constrained High Resolution Radon decomposition is performed at various frequencies in which the Radon decomposition at a given frequency is constrained as a function of the Radon decomposition at at least a lower frequency. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope of meaning of the claims.

Abstract: A method and computer system of processing seismic data is presented. A high-resolution Radon transform is defined for use on seismic data. The high-resolution Radon transform is regularized using a semblance measure of the seismic data. The seismic data is processed using the high-resolution Radon transform to enhance desirable features of the seismic data. A tangible representation of the processed seismic data is presented. The semblance measure of the seismic can include a semblance measure along a dimension of the seismic data.

Abstract: The invention concerns a method for detecting geological discontinuity in an environment using an optical flow. The method includes the steps of selecting in the seismic block a section containing at least one discontinuity. The section constitutes a seismic image. The method includes computing a rough optical flow on the seismic image to obtain a first representation of an optical flow wherein the discontinuity constitutes a moving front. The method also includes smoothing, by a non-supervised dynamic cluster process, the optical flow representation so as to obtain a second optical flow representation wherein the discontinuity shows accentuated contrasts.

Abstract: A method of reducing the computer calculation time of a superposition is disclosed. A computing device having an input unit, an output unit, a memory unit, and an operation unit, is used to calculate the model superposing the function with shifted value of the variable. The model operator is formed by superposing a delta function in the same manner as the superposition of the function. The convolution of a model operator and the function is determined to thereby reduce the calculation time of the model superposing the function with the shifted value of the variable.

Abstract: The present invention relates to a method of controlling the quality of seismic data that has been migrated using the generalized Radon transform, the method serving to pass between a seismic data space and a migrated image space, in which method a parameter table is calculated giving, for a seismic wave going from a point of the image to a source or a sensor, its path length, its travel time, and the angles of incidence of the wave at the beginning and at the end of the path, and in which correspondence is established between at least one zone of a first one of said two spaces and at least one zone of the second space, by using said parameter table to fill in a correspondence table QCimage.

Abstract: A seismic signal is represented as a combination of a geologic signal and a noise signal. The representation of the seismic signal is decomposed into a linear combination of orthonormal components. One or more components are identified in which the geologic signal and the noise signal are uncorrelated. The noise signal is expanded as a product of an unknown noise amplitude modulation signal and a known noise spatial periodicity signal at the identified components. The expansion is solved for an estimate of the noise amplitude modulation signal at the identified components. The noise signal is estimated by multiplying the estimated noise amplitude modulation signal by the noise spatial periodicity signal. The estimated noise signal can be removed from the seismic signal to generate an estimate of the geologic signal.

Abstract: This invention relates to using elastically nonlinear seismic imaging methods, to identify the bypassed hydrocarbons and the movement of the reservoir fluids in the reservoir due to injection and production processes. Time-lapse seismic recording is used to monitor the changes in the hysteretic nonlinear behavior of the pore fluids in the reservoir rocks. Since the nonlinear hysteretic behavior of the saturated reservoir rock generates harmonics of the primary seismic signal that propagates through it, the measurement of these harmonics is used to determine the changes in the reservoir fluids due to hydrocarbon production over time.

Abstract: The invention relates to a vibroseis analysis method in which frequency-sweep signals (10) are emitted into a subsurface, the signals reflected on the substrata of such a subsurface (10, 20) are logged and the logged signals are processed, a method in which the harmonics (20) of the fundamental signal (10) initially emitted are eliminated from the logged signals, by applying the steps consisting in: a) providing a time/frequency plot, showing the respective contributions of the fundamental (10) and of the harmonics (20) in the logged signal, b) providing a time/frequency plot also showing these contributions of the fundamental (10) and of the harmonics (20) in the logged signal, this plot having been stretched in the direction of the frequency axis such that the fundamental (10) of this plot is over the location of a harmonic (20) chosen from the plot; c) adapting the power amplitude of this stretched plot to make this amplitude correspond to that of the said chosen harmonic (20) of the plot; d) subtracti