Abstract: A method for forming a prograde kinematic model allowing reproduction in 3D intermediate geometries of geologic objects of an underground zone such as a sedimentary basin, from an initial state to a current state. A representation of the current geometry of the geologic objects of the zone is formed by interpretation of acquired data obtained by seismic exploration, by in-situ measurements and by observations, then each geologic object is subdivided into layers separated by deformation interfaces. Each one of the layers is defined by means of a grid pattern into a series of hexahedral volume elements. Tectonic deformations are then applied separately and successively to each series of volume elements of a layer in relation to an underlying layer while conserving the thickness and the surface area of an intermediate neutral surface in each volume element.

Abstract: The instant invention teaches an improved frequency domain based method of generating attributes from 2D or 3D seismic data. The central idea of the instant invention is that if a curve characterized by constant coefficients is fitted to a short-window Fourier transform amplitude or phase spectrum, the coefficient estimates that are obtained thereby can be used as seismic attributes for use in detecting changes in subsurface properties that may be associated with the generation, migration, accumulation, or presence of hydrocarbons. Since it is well known that many subsurface structural and stratigraphic features alter the frequency characteristics of seismic waveforms passing therethrough, the instant invention provides a new way to search through large numbers of seismic traces for frequency changes that may be correlated with subsurface features of exploration interest.

Abstract: In one embodiment the invention comprises a method for receiving an acoustic wavefield beneath the surface of the water in which at least a portion of an acoustic wavefield is received at a first position, at least a portion of an acoustic wavefield is received at a second position, and at least a portion of an acoustic wavefield is received at a third position. The first position, the second position and the third position are triangularly positioned relative to one another. The first position is not directly above or below the second position or the third position, and the second position is not directly above or below the third position.

Abstract: A method is provided to process system test data to determine certification parameters of the system based on the test data. For a torpedo launch system, the velocity data is generated by a Pressure/Velocity/Displacement housing interfaced with a computer based data acquisition system and known launch system and test parameters, such as sample rate, muzzle exit length, time of acquisition, decimation factor and low pass cutoff frequency are provided as inputs. The method forces assigns a value of zero to any data less than a predetermined threshold in order to eliminate non-zero levels contributed by ambient noise. The method then passes the data through a filter chosen to agree with hand fit smoothing methods, so as to obtain a smoothed velocity profile. The smoothed data is processed to obtain and display an acceleration profile and a displacement profile, as well as data points for peak acceleration, time at peak, acceleration pulse width, muzzle exit velocity and time at exit.

Abstract: In one embodiment the invention comprises a system for controlling the quality of seismic data acquisition substantially near the acquisition site. A scattered acoustic wavefield is generated and at least a portion of the scattered acoustic wavefield is received. At least a portion of the scattered acoustic wavefield is substantially deghosted relatively near the acquisition site and the quality of the substantially deghosted scattered acoustic wavefield is evaluated.

Abstract: A method and apparatus are disclosed for attenuating noise in seismic data including a plurality of input traces. The method includes transforming the seismic data from the space-time domain into the slant-stack domain. Seismic data having a preselected characteristic is excluded when the transforming into the slant-stack domain. The transformed data is inverse transformed from the slant-stack domain into the time space domain. The method and apparatus may include anti-alias filtering the seismic traces. The method and apparatus may include p-anti-alias filtering seismic traces.

Abstract: A non-rigid method of matching two (12, 14) or more sets of seismic data signals obtained from the same subsurface area involving the steps of decomposing (20) the sets of seismic data signals into sample sets, generating displacement vectors (26) indicating directions and amounts samples from one sample set may be translated to better match samples from the other sample set, and translating (30) samples along the displacement vectors to produce a seismic image of the subsurface area. This method is particularly adapted for use in analyzing time-lapsed seismic images of petroleum reservoirs to monitor the movement of fluids within the reservoirs.

Abstract: A method of designing and applying filters for geophysical time series data comprising obtaining a plurality of spatially related geophysical time series and transforming the time series using a wavelet transformation. The wavelet transformation coefficients may be organized into a plurality of subband traces. The method includes modifying one or more transform coefficients within a plurality of the subband traces or within all but one of the subbands of traces and then inverting the subband traces using an inverse transform to produce a filtered version of the transformed portion of the geophysical time series. The method allows for design and analysis of non-stationary filters and filter parameters in untransformed data space. Non-stationary signals may be filtered in all or in windowed portions of the geophysical time series data.

Abstract: A method of seismic surveying and seismic data processing using a plurality of simultaneously recorded seismic-energy sources. An activation sequence for each of said plurality of seismic energy sources may be determined such that energy from seismic sources may be recorded simultaneously and seismic energy responsive to individual seismic sources separated into separate source records. The seismic sources are activated using an activation sequence, the recorded seismic energy in the shot recordings may be separated into source recordings responsive to individual seismic sources. The source records may be derived from the shot records using a combination of shot record summations, inversions and filtering.

Abstract: A method for processing data from dual sensor receivers to produce a combined seismic trace. A first seismic trace is received from a geophone and second seismic trance from a hydrophone in a dual sensor receiver. This first and second seismic traces are transformed into a first and second seismic spectrum. The seismic spectrums are deghosted to obtain deghosted spectrums. The seismic spectra may be added to obtain a deghosted third spectrum. An inverse power is computed for each of the deghosted spectra. The inverse powers for each deghosted spectra are divided by sums of the deghosted spectra to obtain diversity filters. The first and third diversity filters are applied to the first seismic spectrum to obtain a scaled first seismic spectrum. The other scaled spectra are formed in a like manner. The diversity scaled seismic spectrum is inversely transformed to obtain the combined seismic trace.

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: A method of stacking seismic traces including the steps of deriving a representation of the noise component of each of the seismic traces; deriving an indication of the correlation between the noise components from the representations of the noise components, and producing a stacked seismic trace by combining the seismic traces in proportions derived from the correlation indications. The method can be used to produce stacked seismic traces having improved signal-to-noise ratios compared to conventionally stacked seismic traces. The preferred embodiment of this method is sometimes referred to as “covariant” stacking, because the weighting factors derived depend on the covariance of the noise components of their constituent traces.

Abstract: A process for analyzing, decomposing, synthesizing and extracting seismic signal components, such as the fundamental of a pilot sweep or its harmonics, from seismic data uses a set of basis functions. The basis functions may be any of the harmonics or other components derived from the pilot sweep. These basis functions are modulated with the data being analyzed. The resulting data output from the modulation are then low-pass filtered so that the instantaneous amplitude and differential phase of the particular signal component to be synthesized may be computed. Each targeted component is then synthesized and the result subtracted from the remaining data.

Abstract: A method for imaging seismic data and eliminating noise and error in the resulting image is disclosed. In this method seismic data that has undergone downward extrapolation is corrected by applying Li-correction at regular depth intervals. The Li-correction is applied using Phase Shift Plus Interpolation Techniques. In a preferred embodiment tapering is applied during the Li-correction to further eliminate noise associated with large dips.

Abstract: A system and method for attenuating noise in vibroseis data acquisition. In particular, according to the invention, several preferred methods are discloses that are particularly useful for attenuating noise in seismic data acquired by slip sweep vibroseis techniques. The techniques disclosed involve band-splitting in the time-frequency domain using mirror-filtering, such as a quadrature mirror filter. A noise estimate is made according to which the data is normalized and summed. The time frequency data then reconstructed and transformed back into time domain for further processing.

Abstract: A method for spectral balancing of near- and far-offset seismic data, whereby velocity and offsets are determined for the seismic data. First, an NMO stretch compensation filter is created by the following steps. A frequency spectrum of the near-offset seismic data is estimated and a stretch factor &bgr; is calculated for the frequency spectrum, using the velocity and the offsets. A stretched frequency spectrum of near-offset seismic data is calculated, based on the stretch factor &bgr;. The frequency spectrum of near-offset seismic data is divided by the stretched frequency spectrum of near-offset seismic data, generating a first frequency response filter. High frequency gain is limited in the first frequency response filter, generating a first gain-limited filter. The first gain-limited filter is convolved with a low pass filter, generating the NMO stretch compensation filter. Then the NMO stretch compensation filter is applied to the seismic data.

Abstract: A swath of marine seismic data is acquired using a plurality of receiver lines, at least two near sources and at least one far source. Lines of data corresponding to the far seismic source are augmented to produce additional lines of interpolated and/or extrapolated seismic data that are equivalent to that which would be produced by a second far source. This makes it possible to obtain fill coverage seismic data with a shorter cable length and also increases the acquisition speed relative to an acquisition method using two near and two far seismic sources.

Abstract: A method and apparatus for acquiring high resolution 3D marine seismic data using at least two seismic streamers which are generally parallel to one another longitudinally, and offset from one another in both the vertical and horizontal plane. In one embodiment, the acquisition method uses a vertically staggered source array which is operated using end-fire principles as described below. A processing method is applied for reducing the effect of receiver signal ghosts on the processed signal, thereby allowing the seismic array to be towed deeper without reducing the effective bandwidth of the processed seismic signals. In another embodiment, a vertically staggered source array is utilized. Such that the array provides for the removal of source signal ghosts from the processed seismic and thereby complement the quasi-over under receiver array to synergistically provide for removal of all signal ghosts.

Abstract: Structural and stratigraphic discontinuities are identified in a 3-D volume of seismic data samples, by first selecting a plurality of directions containing a primary direction and at least one secondary direction. Next, one-dimensional, two-trace first discontinuity values are calculated along the primary direction for each seismic data sample in the 3-D data volume. Next, a series of sequentially less restrictive thresholds is defined, such that a significant portion, preferably at least approximately 10%, of the first discontinuity values satisfy the first threshold. This significant portion of first discontinuity values is then stored in an output discontinuity volume at the corresponding sample locations. The following steps are repeated for each remaining data sample until that sample has a value stored at the corresponding sample location in the output discontinuity volume.

Abstract: A method for identifying optimal seismic energy source configurations for a selected seismic survey area. Physical properties of the surface or near-surface soil or rock are assessed and are tested to determine the response of such soil to energy source characteristics and geometries. A test model for a source is generated and is projected to create a far-field seismic response model. A seismic event is initiated within the survey area to measure seismic data, and such measured data is compared against the far-field seismic response model. Differences can be assessed to permit modifications to the model, and the model can be tested for different types and configurations of seismic source energy sources.

Abstract: In one embodiment of the present invention, a method for processing a scattered acoustic wavefield is provided. The scattered acoustic wavefield is received by at least two receivers. These receivers are offset and located at approximately the same depth. The method comprises transforming the scattered acoustic wavefield to the frequency domain. The method also comprises transforming the scattered acoustic wavefield from the frequency domain to the spectral domain. The method also comprises deghosting the scattered acoustic wavefield in the spectral domain. The method further comprises transforming the substantially deghosted transformed acoustic wavefield to the space-time domain.

Abstract: A method of processing seismic data comprising obtaining a seismic data volume covering a predetermined volume of earth; determining for each voxel in the seismic data volume the local orientation of the seismic data; determining for each voxel whether there is an edge in its neighborhood; and carrying out a smoothing operation on each voxel in the seismic data volume, wherein the direction of the smoothing operation is the local orientation of the data and wherein the smoothing operation does not go over the edge, to obtain a processed seismic data volume in which the quantity assigned to each voxel in the processed data volume is the result obtained by carrying out the smoothing operation in that voxel in the seismic data volume.

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.

Abstract: A method for eliminating the tool mode signal from a received combined signal including both tool mode and formation mode components, uses a signal from a reference receiver that is consists primarily of the tool mode signal. A transfer function is derived relating the time reversed combined signal and the time reversed reference signal and used to predict the tool mode portion of the combined signal. Subtracting the predicted tool mode portion of the combined signal from the combined signal gives an estimate of the formation mode component.

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 is disclosed for attenuating acquisition geometry imprint in seismic data. The method includes raising amplitudes of the data to a predetermined power, calculating weights, selecting a time slice of the seismic data and the weights, scaling the data with the weights, stacking the scaled data, stacking the weights, and dividing the stacked scaled data by the stacked weights.

Abstract: A method and system for identification of primary seismic events in the presence of non-primary events (e.g. multiples) is provided in which coherency filters are used to avoid attenuation of primary events when attenuating multiples.

Abstract: Methods for processing sonic logging data obtained from a logging tool having an array of R receivers, includes selecting a sub-array size of Rsb receivers where Rsb<R; calculating the number of sub-arrays Nsb possible from the array of R receivers; identifying one receiver Rref in the array to serve as a reference receiver for each sub-array; processing data in the slowness-time plane for each sub-array with respect to the reference receiver Rref; and stacking the processed data in the slowness-time plane for all sub-arrays.

Abstract: A method and apparatus are disclosed for attenuating noise in seismic data including a plurality of input traces. The method includes transforming the seismic data from the space-time domain into the slant-stack domain. Seismic data having a preselected characteristic is excluded when the transforming into the slant-stack domain. The transformed data is inverse transformed from the slant-stack domain into the time space domain. The method and apparatus may include anti-alias filtering the seismic traces. The method and apparatus may include p-anti-alias filtering seismic traces.

Abstract: A method of compensating for seismic receiver motion in a marine seismic survey wherein at least one receiver is towed behind a moving seismic vessel comprises producing an acoustic energy wave at a seismic source, and recording the reflection arrival time t2 of the acoustic energy wave at the one receiver. The offset x between the source and the one receiver is determined. The normal moveout velocity V for the acoustic energy, and the velocity VB of the seismic vessel, are also estimated. A corrected reflection arrival time t1 of the acoustic energy wave is then determined by applying a time correction to the recorded reflection arrival time t2. The time correction is a function of the offset x, the normal moveout velocity V, and the velocity VB of the seismic vessel. The method is applicable to a plurality of receivers, whether the receivers are arranged in a single sensor acquisition system or hardwired to form receiver groups.

Abstract: A method of determining acoustic properties of borehole earth formations, comprising: (a) transmitting acoustic energy from a transmitter location and receiving acoustic energy (a portion of which traveled through the formations) at a plurality of receiver locations in the borehole; (b) deriving data signals from the received acoustic energy; (c) selecting model values of the acoustic properties; (d) producing an intermediate matrix; (e) performing a singular value decomposition on the intermediate matrix to obtain a basis matrix of eigenvectors; (f) deriving a propagator matrix as a function of the model values; (g) producing a reduced propagator matrix from the propagator and basis matrices; (h) producing a test statistic using the data signals and the reduced propagator matrix; and (i) repeating steps (c)-(h) for different combinations of model values, and selecting, as output acoustic property values, the combination of model values resulting in a maximized test statistic.

Abstract: A method of acquiring and processing seismic data involving deploying a number of seismic sensors, actuating a seismic source, receiving seismic signals produced by the seismic source using the seismic sensors, calculating offset distances (44) between the seismic source and the seismic sensors, and (42) producing spatially filtered seismic data from the received seismic signals. The inventive method may be used effectively with receiver arrays having smaller areal footprints and fewer sensors per receiver station location than conventional seismic data acquisition systems. It also allows ground roll and random noise to be effectively attenuated as the seismic data is spatially resampled or prepared for spatial resampling.

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 temporarily 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 and a real arrays.

Abstract: The present invention provides a method of obtaining and processing seismic data to obtain enhanced geophysical maps from pre-existing 3D seismic data. A first set of data is obtained from a vertical seismic profile (VSP) survey and a second set from reverse seismic profile survey by reversing the locations of the sources and receivers of the VSP survey. The two sets of data are combined to determine a transfer function or model, which is then applied to a set of 3D seismic data to obtain a seismic map of the area surveyed for the 3D data.

Abstract: This invention provides a method for analyzing and compensating for the deleterious effects of irregular illumination of the subsurface due to velocity variations in the subsurface and of irregular spatial sampling of seismic data. For a processing operator, like Kirchoff migration for seismic data, a conventional migration operation is carried out. The output points are analyzed for sampling artifacts caused by irregular surface sampling of the data and those due to ray path distortions. An inverse sampling operator or a filtering operator is determined that is related to dip dependent attributes at the image location. Application of the inverse sampling operator or filtering operator along with the migration or other processing operator to the seismic data compensates for the effects of irregular sampling and of raypath distortion.

Abstract: A method for reducing noise and for deriving new data from seismic and seismic derived rock property data includes determining a rate of change and direction of rate of change of amplitudes of seismic and seismic derived rock property cubes along microlayer horizons and filtering this data long the microlayer horizons. To facilitate this determination, microlayer horizons can be locally rotated around each microlayer horizon definition point. The data determined for the microlayer horizons are sequentially organized in time whereupon a display of the microlayer horizons can be sequentially stepped through to view the output data of each microlayer horizon.

Abstract: A method for suppressing noise in a common depth point gather of seismic data traces is disclosed in which noisy data traces are detected and muted by a sequence of data processing steps prior to making a final stack of the data traces.

Abstract: An improved method for the processing of data of seismic traces for the geophysical interpretation of the earth's subsurface employs deconvolution based on fractionally integrated white noise. A generalized form of deconvolution that more accurately models the earth's reflectivity applies the steps of (1) estimating the process order of the fractionally integrated noise model; (2) computing one or both of two correction filters based on the fractionally integrated noise model; and (3) applying one or both of the filters to the deconvolution processing of the seismic data. The resulting graphical displays based on the deconvolution processing more accurately portray the reflectivity and provide improved wavelet compression and signal resolution, thereby aiding in, and improving the interpretation of the subsurface strata.

Abstract: Seismic acquisition apparatus comprising a plurality of detectors (s1, s2, etc.) each constituted by one or more seismic sensors, combiner means which generate at least one seismic trace corresponding to a group of detectors by combining the signals output thereby, and memory means for storing the seismic traces generated in this way, the apparatus being characterized in that it includes seismic preprocessor means (&mgr;P1, &mgr;P2, etc.) for re-phasing the signals output by the detectors prior to the signals being combined and/or prior to accidental noise on said signals being eliminated.

Abstract: A speaker system is used in conjunction with a surface seismic source that may be vibratory or impulsive. A speaker system having one or more speakers produces a sound signal that propagates primarily through the air and is received by microphones near the seismic spread. A transfer function between the microphones and the geophones in the seismic spread is determined from the speaker signal and used to filter out the airborne noise produced by the surface seismic source. The source may include or more vibrators that may be operated in a predetermined phase-relationship. The noise-attenuated signals may then be processed to separate out the contributions of the individual sources. Another embodiment of the invention uses accelerometer measurements of the reaction mass or the base plate of the vibrators or combination of the two measurements to invert the noise-attenuated signals.

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 correcting seismic amplitudes for geometrical artifacts resulting in non-uniform illumination of reflector surfaces. The illumination is calculated for each offset as a function of spatial position. The amplitudes are scaled by a scale factor which may be the reciprocal of the illumination. Data considered to be poor quality due to low illumination may be discarded, and the amplitudes scaled further to compensate for the discarded data.

Abstract: Structural and stratigraphic discontinuities are identified in a 3-D volume of seismic data samples in the presence of reflection dip, by first selecting a primary and at least one secondary direction in the volume of seismic data samples. Next, skeleton patches are identified in the volume of seismic data samples, where the skeleton patches comprise groups of connected seismic samples representing seismic horizons in the volume of seismic data samples. Apparent dip is calculated in the primary and secondary directions at each data sample within the identified skeleton patches, creating a primary and secondary direction dip volumes, respectively, at corresponding data sample locations. A filter is applied to the primary direction dip and secondary direction dip volumes to fill in values at the data sample locations not within the identified skeleton patches.

Abstract: In a preferred embodiment the invention comprises a method of processing well log data which includes evaluating the said well log data to identify variations in the well log data which are indicative of thin beds of a selected thickness, and reducing the magnitude in the well log data of the identified variations by a magnitude related to the selected thickness.

Abstract: A method for migrating seismic data is disclosed in which seismic traces recorded by a plurality of receivers are separated into offset bands according to the offsets of the traces. The data in each offset band is then migrated according to a downward continuation method. The downward continuation method includes the calculation of a constant that is not dependent on the value of the wave field. The constant is used to calculated the wave field for all offset bands for a given z level, thereby reducing time and computation resources consumed by the migration of the offset bands. Following the downward continuation, an imaging condition may be applied to produce a seismic image.

Abstract: A method is disclosed for processing of dual sensor OBC data that corrects for angular incidence angle, corrects for estimated reflectivity, and combines the corrected sensor traces using an optimal diversity scaling technique. In one embodiment, the disclosed method takes seismic traces from a geophone and a hydrophone, corrects the geophone trace for the incidence angle, determines diversity filters for optimally combining the geophone and hydrophone traces, applies the diversity filters, estimates a reflectivity coefficient for the ocean bottom (potentially for different angles of reflection), scales the geophone data according to the reflectivity, and re-applies the diversity filters to obtain a combined trace. The combined trace is expected to have various artifacts eliminated, including ghosting and reverberation, and is expected to have an optimally determined signal-to-noise ratio.

Abstract: A method for efficiently and accurately producing filter coefficients for wavefield extrapolation which is particularly useful for migrating seismic data using a multiprocessor parallel computer as provided. In 3D seismic migration, the techniques have been developed for 3D processing using 1D extrapolation filters. The present invention uses a Remez-type approximation for developing such extrapolation filters which increases image quality or reduces processing time, or both. Additionally, the method provides an automated method for producing such extrapolation filters which is particularly useful in parallel seismic migration because of the large number of extrapolation filters which must be produced. The automated method of generating filters sets a frequency transition band where the amplitude is specified to be monotonically decreasing which insures stable filter design.

Abstract: Lines of existing data are extrapolated to provide additional lines of seismic data by using small inline gates of existing cables. At each frequency slice of a space gate on the existing cables, a 2-D prediction error filter that can predict the data in forward and backward directions is designed. A prediction filter is obtained from the prediction error filter and applied to a cable at an edge of the space gate to predict a first missing cable. By repeating this process using overlapping inline gates, overlapping inline gates of the extrapolated cables may be obtained. By suitable weighting of the inline gates of the extrapolated cables, a complete cable length is extrapolated. The process may be repeated using the first extrapolated cable in the derivation to give additional extrapolated cables. The invention may be used for interpolating cables of dealiased cables between existing cables using a masking and filtering operation in the frequency-wave number domain.

Abstract: A method for compensating for amplitude loss in a set of seismic traces, where the amplitude loss is caused by shallow attenuation anomalies. Attenuation factors are calculated from first-arrival amplitudes for long-offset seismic data traces. Those factors are calculated by numerical methods, using matrix inversion and iteration. Those factors are used to adjust upward the amplitudes of all later-arriving seismic traces. Frequency dependent attenuation is treated by dividing the seismic traces into frequency ranges using band-pass filters, then using the above-described method within each frequency range after which the adjusted amplitudes are recombined. Amplitude variations caused by inconsistencies in the data acquisition system, such as a source strength variation, are also treated by a similar approach.

Abstract: The invention comprises a method for processing crosswell seismic data from a region of the earth's subsurface generated by transmitting a seismic signal from a plurality of source positions within at least one borehole within said region and detecting said seismic signal at a plurality of receiver positions in at least one borehole within said region. In a preferred embodiment, the seismic data is utilized to develop a model of raypaths traveled by seismic signals from said source positions to said receiver positions, and these raypaths are evaluated to determine if the seismic signal traveling along the raypaths traveled as a headwave for at least a part of the transmission path between the source position and the receiver position. Raypaths along which the seismic signals traveled as headwaves are deleted from the model, and a profile representing a property of the region of the earth's subsurface is then prepared utilizing the residual raypaths.