Abstract: Systems and methods for acquiring seismic data are described, one system comprising one or more seismic sources, a plurality of sensor modules each comprising a seismic sensor configured to sample analog seismic data, each module comprising a comparing unit comprising software; wherein the software in each module tests clock quality by running a sigma-delta modulator from two different clock sources in the node and compares a noise-floor of the modulator when using the different clocks.

Abstract: The technologies described herein include systems and methods for reducing noise in seismic data. More specifically, implementations may determine an amount of over-sampling for a frequency range of seismic data. Then, implementations may determine frequency bands based on the over-sampling. For each frequency band minimum-noise seismograms may be selected from consecutively occurring blocks of seismograms, and the remaining seismograms within each block may be discarded. The minimum-noise seismograms may then be used to reconstruct the discarded seismograms. The reconstructed seismograms may contain less noise than the original seismograms and, consequently, the seismic data may contain less noise.

Abstract: Diagonal gather trace interpolation systems and methods are disclosed. In some embodiments, the method includes obtaining seismic traces from a marine seismic survey performed using typically two seismic sources fired in a flip-flop pattern. The seismic traces are processed in common field file trace groups from each cable by performing trace interpolation in opposing diagonal directions. Among other things, diagonal trace interpolation may improve azimuthal regularization. In any event, the disclosed interpolation methods maintain spatial bandwidth increased spatial resolution with increased inline and crossline sampling components. Diagonal gather trace interpolation exploits reduced input trace separation to provide improved stability and detection of a greater range of formation dip angles. After interpolation and regularization, the seismic traces may be imaged and interpreted for improved seismic exploration and monitoring.

Abstract: A method for seismic surveying includes disposing a plurality of seismic sensors in a selected pattern above an area of the Earth's subsurface to be evaluated. A seismic energy source is repeatedly actuated proximate the seismic sensors. Signals generated by the seismic sensors, indexed in time with respect to each actuation of the seismic energy source are recorded. The recorded signals are processed to generate an image corresponding to at least one point in the subsurface. The processing includes stacking recordings from each sensor for a plurality of actuations of the source and beam steering a response of the seismic sensors such that the at least one point is equivalent to a focal point of a response of the plurality of sensors.

Abstract: Method for updating a velocity model (926) for migrating seismic data using migration velocity scans with the objective of building a model that reproduces the same travel times that produced selected optimal images from a scan. For each optimal pick location (914) in the corresponding test velocity model (916), a corresponding location is determined (922) in the velocity model to be updated, using a criterion that the travel time to the surface for a zero offset ray (918) should be the same. Imaging travel times are then computed from the determined location to various surface locations in the update model (924), and those times are compared to travel times in the test velocity model from the optimal pick location to the same array of surface locations. The updating process consists of adjusting the model to minimize the travel time differences (934).

Abstract: In a first aspect, a method for use in a time lapse, marine seismic survey includes accessing a set of baseline seismic data; accessing a set of acquired, time lapse seismic data; and interpolating a set of time lapse seismic data from the baseline seismic data and the acquired time lapse seismic data, at least one of the baseline seismic data and the acquired time lapse seismic data being multicomponent data. In other aspects, a program storage medium is encoded with instructions that, when executed by a computing device, perform the above method and a computing apparatus programmed to perform one or more of such methods.

Abstract: A technique is provided for identifying an internal multiple generator in a subterranean structure. The technique includes injecting wavefields at different levels in the subterranean structure, where the different levels are proximate a predicted location of the internal multiple generator. Wavefields induced by the injected wavefields are recorded and the effect of the internal multiple generator based on the recorded wavefields is determined.

Abstract: A method and apparatus for correcting an input seismic trace. The method includes receiving the input seismic trace and creating a t by Q gather using the input seismic trace, where t represents traveltime, Q represents absorption parameter, and the t by Q gather has traveltime as the vertical axis and a ratio of t and Q as the horizontal axis. The ratio of t and Q is referred to as R. The method further includes applying an interpolation algorithm to the t by Q gather to derive a corrected input seismic trace.

Abstract: A method and apparatus for a method for generating an estimated value of absorption parameter Q(t). In one embodiment, the method includes receiving an input seismic trace, applying a time variant Fourier transform to the input seismic trace to generate a time variant amplitude spectrum of the input seismic trace, dividing the natural logarithm of the time variant amplitude spectrum by ??f, and performing a power series approximation to the result with an index starting from one to generate an estimated value of R(t). R(t) is a ratio between traveltime t and the absorption parameter Q(t). The method further includes dividing t by R(t) to generate the estimated value of the absorption parameter Q(t).

Abstract: A P-wave slowness-polarization data set resolving P-wave slowness against P-wave polarization angle is extracted from a multi-offset vertical seismic profiling data set. A function relating P-wave polarization angle to P-wave slowness, and being dependent on at least three free parameters, wherein in at least two of these free parameters information of shear wave velocity is absorbed together with one or more anisotropy parameters that characterize formation anisotropy is selected, and regression values found for the at least three free parameters by fitting the selected function to the P-wave slowness-polarization data set. The regression values may be utilized in a method of producing a mineral hydrocarbon fluid from an earth formation.

Abstract: A method and apparatus for generating a seismic source signal are provided for generating energy in the form of a plurality of time sequence vibratory signals, the vibratory signals being partitioned as a function of time and/or frequency, wherein each of the plurality of signals comprises a distinguishing signature. The partitioned vibratory signals are emitted into a terrain of interest as seismic source signals for conducting a seismic survey.

Abstract: This invention pertains to the extraction of the slowness dispersion characteristics of acoustic waves received by an array of two or more sensors by the application of a continuous wavelet transform on the received array waveforms (data). This produces a time-frequency map of the data for each sensor that facilitates the separation of the propagating components thereon. Two different methods are described to achieve the dispersion extraction by exploiting the time frequency localization of the propagating mode and the continuity of the dispersion curve as a function of frequency. The first method uses some features on the modulus map such as the peak to determine the time locus of the energy of each mode as a function of frequency. The second method uses a new modified Radon transform applied to the coefficients of the time frequency representation of the waveform traces received by the aforementioned sensors.

Abstract: There is provided herein a system and method of acquiring, processing, and imaging transient Controlled Source ElectroMagnetic (t-CSEM) data in ways that are similar to those used for seismic data. In particular, the instant invention exploits the time-distance characteristics of t-CSEM data to permit the design and execution of t-CSEM surveys for optimal subsequent processing and imaging. The instant invention illustrates how to correct t-CSEM data traces for attenuation and dispersion, so that their characteristics are more like those of seismic data and can be processed using algorithms familiar to the seismic processor. The resulting t-CSEM images, particularly if combined with corresponding seismic images, may be used to infer the location of hydrocarbon reservoirs.

Abstract: A system and method is provided that uses signals from a plurality of seismic sensors to define an acoustic lens for subsurface imaging. More specifically signals provided by an array of sensors/geophones may be utilized to form an acoustic lens that can be focused on a subterranean point by properly adjusting the signals recorded at each sensor prior to summation of those signals. To form such an acoustic lens, each of the seismic sensors is moved onto a hypothetical acoustic lens surface (e.g., spherical surface) having a focal point located on the subterranean point of interest in order to calculate a time delay for each signal. Once the signals for each sensor is time-delayed, information in the time-delayed signals, which is received from the point of interest, may be temporally aligned. Accordingly, the time delayed signals may be combined to generate reflection information for the point of interest.

Abstract: A technique includes generating one or more sweep sequences for one or more seismic vibrators for a seismic survey and evaluating a cost for the sequence(s). The technique includes perturbing the sequence(s) and continuing the evaluation and perturbing until the cost is within a limit or a maximum number of perturbations is reached.

Abstract: Earth analysis methods, subsurface feature detection methods, earth analysis devices, and articles of manufacture are described. According to one embodiment, an earth analysis method includes engaging a device with the earth, analyzing the earth in a single substantially lineal direction using the device during the engaging, and providing information regarding a subsurface feature of the earth using the analysis.

Abstract: A method for creating an enhanced seismic image is described. Seismic data is acquired from a seismic survey conducted over a subterranean region. The seismic data is transformed into energy components, preferably Gaussian beam components. An earth model is created which is comprised of lens elements. The set of energy components is propagated or migrated through the lens elements to form image components which are combined into a seismic image. A target is identified in the seismic image for image enhancement. Ray tracing may be used to select the trial set of lens elements to be updated and to select a subset of energy components. The subset of energy components is propagated through updated earth model to form updated image components. The seismic image is updated by replacing image components with updated image components which are formed from the subset of selected energy components. This subset is ideally greatly reduced in size relative to the overall number of energy components, i.e., beam components.

Abstract: Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The methods comprise the steps of assembling seismic data into common geometry gathers in an offset-time domain without correcting the data for normal moveout. The amplitude data are then 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 the transformed data 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 determining the existence of and location of hydrocarbon and water fluid contacts by analyzing spatial changes in 3D seismic data. The method begins by obtaining seismic attribute data as a 3D data volume. Then the method derives 3D dip and azimuth as a 3D volume and deriving corresponding 3D reliability volumes or derives responding 3D censor volumes which are representative of portions of the volume within which a reliable dip and azimuth can be determined. A focused subvolume of interest within the 3D data volume is then selected. The method concludes by storing filtered 3D seismic attribute data within the filter half length in each 3D direction along with null values for all non-reliability locations outside the filter half length but within the focused subvolume of interest forming a 3D output volume.

Abstract: The method disclosed is useful for estimating anisotropic properties of an earth formation. The method includes extracting travel time values of components of the acoustic wave induced from a downhole tool and reflected from a boundary bed formation. The method further includes obtaining a travel time ratio of the wave components and using the travel time ratio to estimate the anisotropic properties of the formation.

Abstract: A method and system for seismic data processing utilizes azimuthal variations in the velocity of seismic signals. The system and method utilizes a plurality of seismic energy sources that are located at known positions at the surface of the earth. The seismic energy sources generate seismic signals that propagate downward into the earth. Some of the seismic signals are reflected and diffracted by various sub-surface layers and are returned to the surface of the earth. The returned seismic signals are received by a plurality of receivers. The method includes the step of determining the distance from an energy source to an image point. A fast travel time of the seismic signal from the energy source to the image point is determined, and a slow travel time of the seismic signal from the energy source to the image point is determined. The azimuth angle between the energy source and the surface location of the image point is calculated.

Abstract: Evolution of an hydrocarbon reservoir in the process of producing is carried out by co-analyzing the changes in the propagation times and seismic amplitudes of a seismic wavelet along propagation paths in the ground. A base survey of the reservoir is provided, with a set of seismic traces at a first time T associated to a first velocity field Vb; a monitor survey of the reservoir is provided, the monitor survey being taken at a second time T+?T, with a set of seismic traces associated to the same positions as in the base survey; the monitor survey is associated to a second velocity field Vm.

Abstract: Data processing means are described for calculating an estimated time of arrival of a seismic or microseismic P or S wave at a sensor station, based on a P to S wave velocity ratio, a calculated estimated time of origin of the event and, where the estimated arrival time of a P wave is to be calculated, a picked arrival time of the S wave at the sensor station or, where the estimated arrival time of a S wave is to be calculated, a picked arrival time of the P wave at the sensor station.

Abstract: A method is provided for processing seismic data for interpretation. The method includes recording an original seismic data trace, decomposing the original seismic data trace into a set of predefined wavelets, and reconstructing a seismic data trace from, at least a subset of, the set of wavelets.

Abstract: A method of determining and analyzing spatial changes in the earth's subsurface. The method includes obtaining seismic attribute data as a 3D data volume and obtaining corresponding 3D dip and azimuth as a 3D volume and obtain corresponding 3D reliability volumes or 3D censor volumes which are representative of portions of the volume within in which a reliable dip and azimuth can be determined. A focused subvolume of interest within the 3D data volume is additionally selected. An average for the plurality of vector dips is computed and a flat spot direction vector for each structural dip and a flat spot direction vector dip magnitude is determined. Sequences of distances from each reliability location is defined and interpolated onto the direction of the flat pot direction vector. The sequences of interpolated seismic attribute data is summed and the summed sequences of interpolated seismic attributed data values are stored.

Abstract: A method of imaging in an underground formation one or more steep-sloping geologic interfaces, which are not necessarily in a plane, by forming with primary reflectors, which are not necessarily in a plane, dihedra giving rise to prismatic seismic reflections (double reflections). The geometry of the steep-sloping interface is determined from choosing seismic records of one or more events corresponding to prismatic reflections for different source-pickup pairs of an acquisition device. A new reflection tomography technique is used, wherein introduction of specific constraints guarantees the convergence of the algorithm. The velocity distribution in the geologic formation and/or the geometry of the interface(s) between the sedimentary layers can be known otherwise or determined by means of the method. The method can apply to a formation comprising several different sloping interfaces.

Abstract: The analysis of scattering diagrams of the correlation-type representation theorem in inhomogeneous media is improved by the use of virtual events. Virtual events here are events which are not directly recorded in standard seismic data acquisition, but the assumption of their existence permits the construction, of internal multiples with scattering points at the sea surface.

Abstract: A method of determining and analyzing spatial changes in the earth's subsurface. The method includes obtaining seismic attribute data as a 3D data volume and obtaining corresponding 3D dip and azimuth as a 3D volume and obtain corresponding 3D reliability volumes or 3D censor volumes which are representative of portions of the volume within in which a reliable dip and azimuth can be determined. The gradient of the seismic attribute data in the direction of structural dip is formed using either a dot product methodology or a derivative methodology after interpolation onto the direction of structural dip. At non-reliability locations or locations where no gradient could be meaningfully computed null values are stored. High gradient values in narrow time or depth ranges which are both statistically significant relative to a background level and contiguous designate regions likely to be proximal to a fluid contact or seismic flat spot.

Abstract: A method is disclosed for migrating seismic data which includes determining travel time of a compressional wave from a source location to a scatter point, taking into account ray bending. Travel time of a shear wave from the scatter point to a receiver location is determined, taking into account ray bending at the interfaces between subsurface strata. The determined travel times are then used to migrate the seismic data. In one embodiment, the travel times take account of vertically transversely isotropic media with a vertical symmetry axis.

Abstract: A method of seismic processing for obtaining information on the geophysics of the subsoil includes acquiring seismic traces at at least one point on the surface of the subsoil or in the subsoil, the seismic traces corresponding on each occasion to two perpendicular components of a shear wave emitted into the subsoil and reflected by different interfaces therein; applying a succession of transformations (?) at least to a temporal portion of the traces for each of these assumptions, determining the value of a parameter representative of the coherence/similarity between the result traces obtained in this way; and election as a function of the values obtained in this way that one of the hypotheses which is considered as being most representative of the subsoil, the two result traces obtained for said hypothesis being compensated traces of the subsoil birefringency.

Abstract: Coherent wave noise energy is removed from seismic data by modeling both the P-wave primary energy and the coherent wave noise energy. The P-wave primary energy is modeled first and then subtracted from the input data. The data with the P-wave primary energy removed is used as the input for coherent wave energy removal. The coherent wave energy is modeled and subtracted from the original input data, i.e. the data input into P-wave primary removal. This leaves a dataset with P-wave primary energy and noise energy not related to coherent waves. This method can be utilized to remove all types of coherent noise with a velocity difference to the desired P-wave primary energy or with a different type of moveout (change of time of arrival with source-receiver distance) such as, for example, linear moveout.

Abstract: A seismic information processing method for determining a property related to an earth subsurface structure includes performing a first processing operation on geophysical information using a computer operating according to a first processing parameter set and generating a first result from the first processing operation. The method may include performing a second processing operation on the first result using the computer and generating a second result from the second operation. At least one measurement point of the second result is evaluated using the computer. The first processing parameter set may be varied at least once to a second processing parameter for processing the geophysical information. The first operation, the second operation and the evaluation are repeated using the second processing parameter set. At least one of the first result, the second result and the evaluation is used for generating the property relating to the earth subsurface structure.

Abstract: Seismic data traces contain noises that may exist in the form of wavelets and be represented by wavelets. A method is established for removing or attenuating the noises in the seismic data traces by removing the wavelets or representing wavelets of noises in the seismic data traces. The method involves three steps. (1) Decomposition of each seismic data trace into a set of time dependent wavelets of different shapes. The obtained wavelets can be named with their dominant frequency or other characteristics of the wavelets. (2) Proper selection of the wavelets to form a new set of wavelets that contains mostly signal wavelets and rejects the wavelets of noises and representing wavelets of noises as mush as possible. This step can also be described as to remove the wavelets of noises and representing wavelets of noises from the obtained set of wavelets from step one and form a new set of wavelets. (3) Composition or reconstruction of a new seismic data trace with the new selected set of wavelets.

Abstract: A method enables the time required to complete a seismic survey and the noises recorded in the seismic data to be reduced. One aspect of the method includes actuating a first vibrator group to start a first sweep at time T0; and a second vibrator group to start a second sweep at time T1, wherein T0<T1<T0+S1+L, where S1 is a sweep time of the first vibrator group and L is a listening time; wherein the time between the first sweep and the second sweep is T1?T0?((n?1)*f1*S1)/(n*(f1?f0)) where n is a natural number, f0 is the lower frequency limit of the vibrator sweep and f1 is the upper frequency limit of the vibrator sweep.

Abstract: There is described a method of moveout or velocity analysis of seismic signals using the steps of obtaining such signals 5 from a plurality of receivers, identifying receiver functions within the acoustic signals, analyzing said receiver functions for velocity or moveout characteristics, using the result of said analyzing step to determine, properties of multiple layers of earth located below said 10 receivers. The analyses can involve the use of representation of the traveltime differences as approximated power series of slowness or horizontal distances. The method is the first to comprehensively deal with a multi-layered earth or velocity model.

Abstract: A method for simultaneously operating multiple seismic vibrators using continuous sweeps (little or no “listening” time between sweeps) for each vibrator, and recovering the separated seismic responses for each vibrator with the earth signature removed. Each vibrator is given a unique, continuous pilot signal. The earth response to the motion of each vibrator is measured or estimated. The vibrator motion records for each vibrator and the combined seismic data record for all the vibrators are parsed into separate shorter records. The shorter records are then used to form a system of simultaneous linear equations in the Fourier transform domain, following the HFVS method of Sallas and Allen. The equations are then solved for the separated earth responses.

Abstract: A process for constructing a three-dimensional geologic model of a subsurface earth volume wherein resolution scales of multiple diverse data types, including seismic data, are accounted for by generating multiple frequency passband models and combining them together to form the complete geologic model. Preferably, a model is generated for each of a low-frequency passband, a mid-frequency passband, and a high-frequency passband. When integrating seismic data into the modeling process, the seismic-frequency passband constitutes the mid-frequency passband model. The process further contemplates updating tentative frequency-passband models through optimization of assigned rock property values in each tentative model according to specified geological criteria. Such optimization is carried out by perturbation of the rock property values in a manner wherein the frequency content of each model is maintained.

Abstract: A method for improving the seismic resolution in the field of petroleum exploration and development, using the steps of: (1) ensuring the depth and the velocity of the low-velocity layer and the high-velocity layer and the characteristic of the frequency spectrum of the seismic wave at the near-surface using the borehole seismic survey; (2) separating the ghost wave from the seismic record in the high-velocity layer using the processing method of the vertical seismic profiling, and improving the SNR of the seismic record of the direct wave at the high-velocity layer using the uphole stacking of the vertical seismic profiling; (3) evaluating the de-convolution operator of the near-surface by the convolution math-physics equation; (4) evaluating the seismic record with high resolution by the de-convolution math-physics equation; (5) providing the band-pass filtering and geologic interpretation to the seismic record with high resolution.

Abstract: A method of and apparatus for processing seismic data. A method of processing seismic data comprising the steps acquiring seismic data in at least two shots that have different source-receiver azimuths from one another, and selecting events arising from interface seismic waves in each shot. The interface wave events are processed to provide information about azimuthal dependence of the velocity of seismic energy in the near-surface of the earth's interior. The invention may be used to process events arising from Scholte waves in marine seismic data, or to processing events arising from Love waves or Rayleigh waves in land seismic data. The method may be applied to seismic data acquired specifically to provide information about the near-surface or to seismic data acquired to provide information about the underlying geological structure.

Abstract: A method and system for processing synchronous array seismic data includes acquiring synchronous passive seismic data from a plurality of sensors to obtain synchronized array measurements. A reverse-time data process is applied to the synchronized array measurements to obtain a plurality of dynamic particle parameters associated with subsurface locations. These dynamic particle parameters are stored in a form for display. Maximum values of the dynamic particle parameters may be interpreted as reservoir locations. The dynamic particle parameters may be particle displacement values, particle velocity values, particle acceleration values or particle pressure values. The sensors may be three-component sensors. Zero-phase frequency filtering of different ranges of interest may be applied. The data may be resampled to facilitate efficient data processing.

Abstract: This invention relates to a method for processing at least two seismic data sets (10, 20), each data set comprising several seismic traces (i, j) grouped by bins (Bi, Bj) and by offset classes (Oi, Oj), the method including the following steps: calculating at least one attribute (a(i, j)) characteristic of a similarity between a first trace (i) of a first data set (10) and a second trace (j) of a second data set (20), selecting or not the first and second traces (i, j) according to a selection criterion applied to the calculated attribute (a(i, j)).

Abstract: Various implementations described herein are directed to estimating stresses and elastic parameters in a formation based on seismic data. In one implementation, wide azimuth seismic data may be used to derive anisotropic elastic parameters. Furthermore, stresses may be calculated using a geomechanical earth model, followed by deriving anisotropic elastic parameters based on the calculated stresses. The anisotropic elastic parameters derived from the wide azimuth seismic data may then be used to modify the geomechanical earth model to improve the prediction of drilling parameters.

Abstract: An apparatus and method for processing a record of seismic traces. The method includes receiving the record of seismic traces in a time-offset domain, transforming the record of seismic traces to a tau-p domain, applying a zero offset inverse Q algorithm to the record of seismic traces in the tau-p domain, and transforming the record of seismic traces back to the time-offset domain.

Abstract: A microseismic method of monitoring fracturing operation or other passive seismic events in hydrocarbon wells is described using the steps of obtaining multi-component s-wave signals of the event; and using a linear derivative of S-wave arrival times of the signals in a first direction, an S-wave velocity and an s-wave polarization to determine at least two components of the S-wave slowness vector.

Abstract: Originating from a novel and an exact algebraic formula for the impulse response of a plane acoustic reflector at zero offset due to a point acoustic source the present invention provides a method for computing an exact impulse response of a plane acoustic reflector at zero offset due to a point acoustic source; and originating from the method, methods for testing and validating algorithms for numerical modeling of seismic reflection, seismic migration and seismic inversion; a method for testing the efficacy of ray-theoretical solution for a given source-reflector configuration; another method for computing zero-offset reflection response of a circular reflector at its central axis; yet another method for validating an interpretation of a reflector as a planar structure; still yet another method for estimating the seismic source-time function when the zero-offset reflection response of a plane reflector is given.

Abstract: A method and system of operating single vibrator source points for seismic data acquisition includes acquiring real-time field survey locations for a first plurality of seismic vibrators, determining at least one geometrical relationship between each of the first plurality of seismic vibrators as a function of the field survey locations, selecting a second plurality of seismic vibrators from the first plurality of vibrators as a function of the at least one geometrical relationship, selecting source parameter data for the second plurality of seismic vibrators as a function of the field survey locations and driving the second plurality of seismic vibrators to propagate seismic energy into the earth. A third plurality of vibrators is selected based on geometrical relationships and associated source parameters are determined based on vibrator locations. Multiple vibrator groups may acquire data continuously without interruption.

Abstract: A method to attenuate unwanted signals in seismic data using seismic interferometry techniques. In one implementation, seismograms may be converted into seismic interferograms. In the seismic interferogram domain, unwanted signals may be attenuated by various techniques, such as muting, filtering and the like. The modified seismic interferograms may then be converted back into seismograms with the unwanted signals having been attenuated.

Abstract: A method and apparatus for filtering data acquired at a plurality of discrete data points is described, using the steps of defining a filter having defined filter values at defined filter points at least partially not coincident with the data points and using the defined filter values at the defined filter points to determine filter values at the data points, thereby correcting the filter to have filter values at filter points coinciding with the data points and filtering the data using the corrected filter.

Abstract: A method and apparatus for processing acoustic data recorded by a subterranean receiver array. The method includes emitting an acoustic signal into a formation, receiving the signal after it passes through the array, and processing the data with semblance and phase velocity processing. Semblance and phase velocity plots are generated and combined into a single plot. The phase velocity processing creates phase separation lines, the phase separation line that crosses the closest contour of the semblance plot is identified. The point where the intersecting phase separation line crosses an associated tool line marks the slowness and travel time that provides maximum coherence.

Abstract: A method for seismic exploration using conversions between electromagnetic and seismic energy, with particular attention to the electromagnetic source waveform used. According to the invention, source waveforms are correlated with reference waveforms selected to minimize correlation side lobes. Line power at 60 Hz may be used to provide a waveform element which may be sequenced by a binary code to generate an extended source waveform segment with minimal correlation side lobes. Preferred binary codes include Golay complementary pairs and maximal length shift-register sequences.