Abstract: Embodiments herein describe techniques for controlling both a vessel and a separate controllable steering element so that a towed device moves along a predefined path or course. A steering system can include a first controller for steering the vessel and a second controller for controlling the steering element, which is in the water and also being towed by the vessel. In one embodiment, the steering system controls the vessel to ensure the steering element does not exceed a control limit.

Abstract: A method for generating a geophysical image of a subsurface region includes defining a computational sub-volume for the geophysical image including a predetermined number of seismic traces of a plurality of seismic traces and a predetermined number of samples per each one of the plurality of seismic traces, generating a data matrix corresponding to a first sub-volume of the subsurface region based on the defined computational sub-volume, the data matrix comprising the predetermined number of samples for the predetermined number of traces of a portion of a seismic dataset corresponding to the first sub-volume. The method also includes estimating a coherence between the predetermined number of traces of the data matrix by performing a sum of a variance of the predetermined number of samples of the data matrix, and assigning the estimated coherence to a location in the geophysical image.

Abstract: The present disclosure discloses a method of obtaining a seismic while drilling signal. The method comprises the following steps: arranging geophones by using a first observation method to obtain a first seismic reference signal and a second seismic reference signal; arranging geophones by using a second observation method to obtain first seismic data; arranging geophones by using a third observation method to obtain second seismic data; comparing the first seismic reference signal with the second seismic reference signal to obtain a first output reference signal, and optimizing the first output signal to obtain a second output reference signal.

Abstract: This disclosure presents processes and systems for estimating a source wavelet from seismic data recorded in a seismic survey of a subterranean formation. In one aspect, a base wavelet is determined based on recorded seismic traces obtained in a seismic survey of a subterranean formation. Processes and systems include a phase-only wavelet based on the base wavelet and the recorded seismic data. An estimated source wavelet is obtained by convolving the base wavelet with the phase-only wavelet. Properties of the subterranean formation are determined based on the estimated source wavelet and the recorded seismic data.

Abstract: A well system includes a fiber optic cable positionable downhole along a length of a wellbore and a reflectometer communicatively coupleable to the fiber optic cable. The reflectometer detects and locates a microseismic event using strain detected in reflected optical signals received from the fiber optic cable. Further, the reflectometer computes a set of spectra for waveforms of the microseismic event. Additionally, the reflectometer aggregates each spectrum from the set of spectra that meet an acceptance threshold to generate an aggregate spectrum. Furthermore, the reflectometer applies a fault source model to the aggregate spectrum to determine a magnitude of the microseismic event.

Abstract: A seabed object detection system is provided. The system can include a receiver array. The receiver array can include a plurality of receivers disposed on a plurality of streamers. The plurality of streamers can include a central port side streamer, a central starboard side streamer, an auxiliary port side streamer and an auxiliary starboard side streamer. The system can include a source array. The source array can include a plurality of sources. The plurality of sources can include a central port side source, a central starboard side source, an auxiliary port side source, and an auxiliary port side streamer. The source array towed during a first pass can define a first path. The source array towed during a second pass can define a second path. The first path can be interleaved with the second path such that the first path overlaps the second path.

Abstract: Methods and apparatuses for obtaining and/or processing slip sweep seismic survey data. The methods compute harmonic weight ratios using two types of data: 1) direct survey data where a harmonic sweep does not overlap with the fundamental component of responses of Earth interior and 2) another set of data representative of fundamental component of responses of Earth interior where the harmonic sweep does overlap with the fundamental component of responses of Earth interior. The set of data representative fundamental component of responses of Earth interior can be extracted from ground force measurements or a different sweep. The harmonic weight ratios using ground force measurements at overlapped frequencies may be calibrated with one or more harmonic weight ratios at non-overlapped frequencies.

Abstract: Provided is elastic reverse-time migration system and method using an absolute value function for improving the quality of subsurface structure images, and more particularly, elastic reverse-time migration system and method using an absolute value function for improving the quality of subsurface structure images capable of minimizing waveform changing by separating wavefields using stress-displacement relationships and improving accuracy of the subsurface structure images by applying the absolute value function to migration images.

Abstract: A method for processing seismic data including contiguous-sweep records corresponding to rotated sweep segments includes attenuating harmonics and generating stacked traces, each stacked trace being a weighted sum of traces corresponding to same location in the subsurface, based on seismic data from different seismic receivers, following plural shots at plural locations.

Abstract: Provided are an apparatus and method for imaging a subsurface using frequency-domain reverse-time migration in elastic medium. The subsurface imaging method represents a frequency-domain imaging condition as convolution of measured data and a partial derivative wavefield. That is, the subsurface imaging method applies a back-propagation algorithm to represent an imaging condition as convolution of a virtual source and a back-propagated wavefield. Then, the subsurface imaging method divides a virtual source vector and the back-propagated wavefield represented by a displacement vector into P- and S-wave potentials through Helmholtz decomposition, thereby providing a new imaging condition.

Abstract: A technique includes generating seismic sweep sequences. Each of the seismic sweep sequences has an associated sweep rate. The technique includes varying the sweep rates to reduce harmonic distortion present in a composite seismic measurement produced in response to the sweep sequences.

Abstract: Seismic data representing the propagation of seismic energy through a geologic volume of interest is processed. The seismic energy propagates through the geologic volume of interest from one or more source locations at or near the geologic volume of interest to one or more detector locations at or near the geologic volume of interest. In processing the seismic data, the seismic energy is modeled as beams (e.g., Gaussian beams). The processing performed (i) corrects for misalignment of the one or more source locations and/or the one or more detector locations with a regular, predetermined mesh, and (ii) steers the seismic data based on the modeled beams.

Abstract: Systems and methods for asynchronously acquiring seismic data are described, one system comprising one or more seismic sources, a plurality of sensor modules each comprising a seismic sensor, an A/D converter for generating digitized seismic data, a digital signal processor (DSP), and a sensor module clock; a seismic data recording station; and a seismic data transmission sub-system comprising a high precision clock, the sub-system allowing transmission of at least some of the digitized seismic data to the recording station, wherein each sensor module is configured to periodically receive from the sub-system an amount of the drift of its clock relative to the high precision clock. This abstract is provided to comply with rules requiring an abstract to ascertain the subject matter of the disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Abstract: Microseismic mapping using buried arrays with the integration of passive and active seismic surveys provides enhanced microseismic mapping results. The system is initially set up by recording seismic data with the buried array installation while shooting a significant portion of the 3D surface seismic survey. The 3D surface seismic survey provides the following data: shallow 3D VSP data from the buried arrays; P-wave and converted wave data for the area covered by the buried array that benefits from the planned data integration processing effort; and microseismic data and associated analysis.

Abstract: Methods and apparatuses are disclosed for replacing the individual receivers used with a seismic interferometry process with an array of seismic receivers and then manipulating the array data in order to measure and modify the typical non-uniform directionality function of the background seismic energy. The non-uniform directionality function is a significant cause of noise with seismic interferometry. Furthermore, the array of receivers may be used to significantly enhance the preferred reflection energy and damp undesirable near surface energy. The directionality function may be modified by using an array of receivers for the virtual source location of seismic interferometry to measure the non-uniform directionality function, generating multiplication factors, and applying the multiplication factors to convert the measured directionality function into a desired directionality function.

Abstract: A seismic data acquisition system includes a controller, a plurality of sensor stations and a plurality of seismic sources. Each sensor station includes a sensor coupled to the earth for sensing seismic energy in the earth. The sensor provides a signal indicative of the sensed seismic energy and a recorder device co-located with the sensor unit that receives and stores the signals. A communication device is co-located with the sensor station and provides direct two-way wireless communication with the central controller. In one embodiment, in-field personnel determine elevation values, or Z values, for the sensor stations and seismic source by accessing a digital elevation model or a look-up table based on the digital elevation model. 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.

Abstract: A method for interpolating irregularly sampled seismic data, including receiving seismic data acquired at irregularly spaced seismic sensors in a survey area, defining a plurality of regularly spaced locations in the survey area, forming an annular ring around one of the plurality of regularly spaced locations, and interpolating the seismic data inside the annular ring to estimate seismic data that would have been acquired at the one of the plurality of regularly spaced locations.

Abstract: Geophysical data representing at least first and second overlapping geophysical spaces may be aggregated. A first set of geophysical data representing the first geophysical space and a second set of geophysical data representing the second geophysical space may be obtained. The second set of geophysical data may be separate and discrete from the first set of geophysical data. The first set of geophysical data may be transformed from a first parametric domain to a third parametric domain, while the second set of geophysical data may be transformed from a second parametric domain to the third parametric domain. The first set of geophysical data may be fused with the second set of geophysical data in the third parametric domain to create a fused set of geophysical data. The fused set of geophysical data may be transformed from the third parametric domain to a fourth parametric domain.

Abstract: Provided are an apparatus and method for imaging a subsurface using frequency-domain reverse-time migration in elastic medium. The subsurface imaging method represents a frequency-domain imaging condition as convolution of measured data and a partial derivative wavefield. That is, the subsurface imaging method applies a back-propagation algorithm to represent an imaging condition as convolution of a virtual source and a back-propagated wavefield. Then, the subsurface imaging method divides a virtual source vector and the back-propagated wavefield represented by a displacement vector into P- and S-wave potentials through Helmholtz decomposition, thereby providing a new imaging condition.

Abstract: To perform noise attenuation for seismic surveying, a sensor assembly is deployed on a ground surface, where the sensor assembly has a seismic sensor to measure seismic waves propagated through a subterranean structure, and a divergence sensor comprising a pressure sensor to measure noise. First data is received from the seismic sensor, and second data is received from the divergence sensor. The first data and the second data are combined to attenuate noise in the first data.

Abstract: Despite full waveform propagation capabilities offered by reverse time migration or inversion, prior art methods can generate spurious events from multiples and therefore are limited to using data without free-surface multiples. By eliminating or largely reducing artificial transmission of multiples, the enhanced reverse time migration or inversion in the present invention can correctly use data that contain free-surface and internal multiples and improve image quality or properties estimation.

Abstract: A technique includes generating seismic sweep sequences. Each of the seismic sweep sequences has an associated sweep rate. The technique includes varying the sweep rates to reduce harmonic distortion present in a composite seismic measurement produced in response to the sweep sequences.

Abstract: A walkaway VSP survey is carried out with receivers located in a borehole under a salt overhang. Redatuming of the multicomponent data to virtual sources in the borehole followed by vector Kirchhoff migration using a simple velocity model provides an accurate image of the salt face.

Abstract: A subterranean structure is characterized using composite seismic response data received from a plurality of sources. Phase encoding is applied to the data in which phase shifts are selected based on frequency variation of noise terms. The phase-encoded data is then migrated and a representation of the subterranean structure is produced according to the migrating.

Abstract: In general, in one aspect, the invention relates to a method for determining properties of a subterranean formation.

Abstract: A method and system of detecting and mapping a subsurface hydrocarbon reservoir includes acquiring seismic data having a plurality of components, applying a data transform to the seismic data to obtain seismic data spectral component maxima and maxima profiles, and recording the maxima or maxima profile in a form for display.

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: A method and apparatus for compensating acquired seismic data for the presence of dipping events are disclosed. The method includes migrating the acquired, unstacked seismic data; and spatially mapping the migrated seismic data to correct their respective offsets while maintaining the angle of incidence to a dipping event. The method may be performed by a programmed computing device or encoded as instructions for a computing device on a program storage medium.

Abstract: The present invention provides a method of performing the time picking step in a VSP (vertical seismic profile) survey. In a preferred embodiment of the invention the time picking step is carried out on a combined three-component amplitude of the received seismic energy, which contains the amplitude of all the seismic energy received at the receiver. The amplitude of the direct pulse in the combined trace will not decrease to zero as the offset of the source is changed, as can be the case for the single-component amplitude of the direct pulse. In a particularly preferred embodiment of the invention, the combined three-component amplitude is calculated by summing the Hilbert instantaneous amplitudes of the x-, y- and components of the seismic data using the equation (I). The present invention also provides two new time picks. One time pick involves finding the maximum positive gradient of A(t).

Abstract: The present invention relates to an apparatus and a method for analyzing the correlation geophysical data and seismic data, physical data monitoring apparatus and method, and an earthquake monitoring method.

Abstract: A system and method of creating a filter for use with locally dense seismic data is disclosed. The method includes obtaining survey geometry characteristics from a locally dense seismic survey. A filter is designed which uses spatial derivatives of the wavefield of order between (1) and the maximum order of spatial derivatives of the wavefield that can be estimated within a group. The filter can be designed so as to separate up/down going components, p/s components, or both up/down and p/s components. Partial derivatives in space and time of the wavefield can be calculated, using, for example, a taylor series expansion as an approximation. The seismic data is filtered by combining estimated near surface material properties, the seismic data, and the calculated partial derivatives.

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: The invention is a statistical method for analyzing exploration data associated with image elements showing physical properties of a complex environment such as subsoil for identifying the spatial relations between image elements. The method comprises successive identification of the spatial structures of the data, separation of these spatial structures with removal of possible redundancies, formation, from initial images, of synthetic images or spatial components that show the spatial structures of the data, providing a typology of the initial images according to the spatial structures shown by the spatial components, and filtering of the initial images in order to suppress the noise and to select one or more identified spatial structures. The method can be used for study of any spatial data, notably in geosciences in order to process seismic images of the subsoil, but also in geography, agronomy, hydrology, geomarketing, etc.

Abstract: A method for identifying faults and stratigraphic features within seismic data without interpreter bias by processing seismic data to identify the minimum difference between seismic traces. Large values of difference are plotted as display attributes for seismic reflection data interpretation for two-dimensional and three-dimensional seismic data. The large values of difference represent faults and stratigraphic features within the seismic data. Dip azimuth and dip magnitude attributes can be generated and displayed as well.

Abstract: A system for, and method of, orienting seismic energy sources and seismic energy receivers to substantially separate a compressional wave from a vertical shear wave. The method includes reflecting a seismic energy from a subsurface interface to produce a reflected seismic energy wave that has a compressional energy and vertical shear energy associated therewith. A first seismic energy receiver is oriented such that it is aligned with an angle of emergence of the reflected seismic energy wave to thereby maximize the vertical shear energy received by a second seismic energy receiver.

Abstract: In a peak detection system having a variable gain amplifier (VGA), a counter is initialized and a countdown is triggered. Each time a qualified peak is detected, the counter is re-initialized. If the countdown is completed, the VGA gain is updated. This method can be used to boost amplifier gain that is too low to generate a qualifying threshold, even while overlooking short periods of very low output.

Abstract: A system and method for periodically providing information about subsurface formations in a marine environment using a non-towed seismic signal source (3) and a static array of seismic signal receivers (4) is disclosed. The seismic signal source (3) comprises a support frame (10) and a line (7) attaching the support frame to a stationary platform (2), wherein the line (7) restrains the support frame (10) in a position that is static in relation to the formation (8). The seismic signal source (3) includes eight air guns (12) attached to the support frame (10) such that the air guns (12) are discharged to provide a tapered, heavy centered, point source seismic signal at a specific location relative to the formation (8) that is reflected to the static array of seismic signal receivers (4) such that changes in the formation characteristics may be observed over time.

Abstract: A computationally efficient semi-recursive Kirchhoff migration algorithm is capable of obtaining accurate images of complex structures in complex geological environments which commonly give rise to multivalued arrivals. The method alternates wave-equation datuming (downward continuation) and Kirchhoff migration. Breaking up the complicated velocity structure into small depth regions allows traveltimes to be calculated in regions where the computation is well behaved and where the computation corresponds to energetic arrivals. Because traveltimes are computed for small depth domains, the effects of multivalued arrivals are implicitly accounted for in the migration and the adverse effects of caustics and headwaves do not develop. The invention can use any simple first-arrival traveltime algorithm, and thus benefits from the computational efficiency, robustness, and simplicity of such algorithms.

Abstract: The method consists in building a common midpoint gather of seismic traces of which the CMP point is said given point, subjecting the traces of this gather to dynamic and/or static corrections, and characterized in that the gather associated with the given point (A) is built by recording four CMP sub-gathers associated with said given point along four angular directions (1 to 4) passing through said given point, and dynamic and/or static corrections are applied to each of the four CMP sub-gathers in order to determine, for each sub-gather, a value of the curvature and/or the velocity optimizing the energy of the trace stack of the corrected sub-gather concerned, the four values thus obtained representing the components of the stacking velocity field desired for each of the reflector elements corresponding to the given point, and characterized by a vertical propagation time t0 with reflection for zero offset.Application in particular to the exploration of a medium with a complex tectonics.

Abstract: Monofrequency continuous wave signals of long duration are used as inputs form sources of known characteristics and location. These signals are reflected off subterranean features and serve to paint the features for display and evaluation. A primary feature is the use of continuous wave, long duration signals as opposed to the standard short pulse technique.

Abstract: A method for seismic data interpretation for the purposes of identification of oil, gas and water accumulation locations and delineation of their contours uses a model of discrete media with inhomogeneous stresses. For a selected reflection horizon, the relative value of overall pressure gradient is calculated on the basis of instantaneous amplitudes and frequencies of seismic signals using a derived relationship between the reflection coefficients of elastic waves and the stress condition parameter. The calculation technique uses estimates of instantaneous amplitudes and frequencies smoothed over the entire seismic horizon or its fragment. A generalized model of normal (lithostatic) pressure is excluded, and the final interpreted parameters have the sense of relative estimates of anomalous pressure caused by basin dynamics.

Abstract: A method of determining the continuity of earth formations between wellbores by analyzing seismic energy imparted to the formations. The energy is imparted to the formations at a plurality of depths in one wellbore and is received at a plurality of depths in another wellbore. Compressional and shear components of the seismic energy received in the other wellbore are separated. A frequency spectrum is determined for the compressional component and the shear component of the seismic energy at each selected depth. Common imparted depth stacks of the compressional components and shear components are assembled at the depths at which the seismic energy is imparted. Common received depth stacks of the compressional components and the shear components are assembled at the selected depths at which the energy is received.

Abstract: A method for producing high vertical resolution seismic images from crosswell data is disclosed. In accordance with one aspect of the disclosure, a set of vertically spaced, generally horizontally extending continuous layers and associated nodes are defined within a region between two boreholes. The specific number of nodes is selected such that the value of a particular characteristic of the subterranean region at each of the nodes is one which can be determined from the seismic data. Once values are established at the nodes, values of the particular characteristic are assigned to positions between the node points of each layer based on the values at node within that layer and without regard to the values at node points within any other layer. A seismic map is produced using the node values and the assigned values therebetween. In accordance with another aspect of the disclosure, an approximate model of the region is established using direct arrival traveltime data.

Abstract: A method for the determination of migration velocities in seismic processing in which a blasting point S is associated with receivers (R.sub.1 to R.sub.n) which are separated by offsets such that in a given speed range, a first set of traces derived from the blasting point and registered on the receivers, and a second set of traces in constant and colinear offset to the first set are migrated. Two migrated images of the part of the site corresponding to the two sets of traces are obtained. The two images are correlated by means of a spatial two-dimensional correlation, the result thereof determining the deviation between the migration used and the investigated velocity. The result is particularly useful in the seismic prospection of a site.

Abstract: A method for identifying faults and stratigraphic features within seismic data without interpreter bias by processing seismic data to identify the minimum difference between seismic traces. Large values of difference are plotted as display attributes for seismic reflection data interpretation for two-dimensional and three-dimensional seismic data. The large values of difference represent faults and stratigraphic features within the seismic data. Dip azimuth and dip magnitude attributes can be generated and displayed as well.

Abstract: A method for generating an unaliased 3-D DMO operator using two dimensional sampling theory to the spatial traverse of the operator as well as to the temporal axis. First a continuous DMO operator is generated along the line segment connecting a source and a receiver directed at an arbitrary azimuth relative to a biaxial output grid. The operator is discretized at spaced-apart sample points along the DMO aperture segment, the spacing being equal to or less than the output grid dimensions. A exponentially tapered sinc filter function is applied to the samples which are then interpolated onto the output grid.

Abstract: A method and apparatus for the exploration of hydrocarbons comprising the steps of: obtaining a set of seismic signal traces distributed over a predetermined three-dimensional volume of the earth; dividing the three-dimensional volume into a plurality of analysis cells having portions of at least two seismic traces located therein; computing outer products of the seismic traces within each cell; forming the covariance matrix for each cell from these outer products; computing the dominant eigenvalue and the sum of the eigenvalues of the covariance matrix of each cell and computing a seismic attribute from the ratio of the dominant eigenvalue to the sum of the eigenvalues of the covariance matrix of each cell; and forming map of the seismic attributes of selected groups of cells.

Abstract: A method for identifying faults and stratigraphic features within seismic data without interpreter bias by processing seismic data to identify the minimum difference between seismic traces. Large values of difference are plotted as display attributes for seismic reflection data interpretation for two-dimensional and three-dimensional seismic data. The large values of difference represent faults and stratigraphic features within the seismic data. Dip azimuth and dip magnitude attributes can be generated and displayed as well.

Abstract: A method of determining the continuity of earth formations between wellbores by analyzing seismic energy imparted to the formations. The energy is imparted to the formations at a plurality of depths in one wellbore and is received at a plurality of depths in another wellbore. Compressional and shear components of the seismic energy received in the other wellbore are separated. A frequency spectrum is determined for the compressional component and the shear component of the seismic energy at each selected depth. Common imparted depth stacks of the compressional components and shear components are assembled at the depths at which the seismic energy is imparted. Common received depth stacks of the compressional components and the shear components are assembled at the selected depths at which the energy is received.

Abstract: A computer-aided method for providing a de-aliased output data set d.sub.L (t,x.sub.L,y.sub.L) from a spatially aliased, three-dimensional, input data set of known seismic signals, a(t,x,y), where L is an interpolator. The known data set is zero-padded by L. The zero-padded data set is zero-masked. The zero-padded data set is divided by a zero-padded, zero-masked data set to provide an interpolation operator H.sub.L. L-1 zero traces are interleaved between the known traces of data set a(t,x,y) to provide a zero-inserted data set c.sub.L ((t,x.sub.L,y.sub.L) whose transform is C.sub.L (m,k.sub.xL,k.sub.yL). The product of (H.sub.L) with (C.sub.L) is (D.sub.L) which is inverse-transformed to provide the desired de-aliased data set d.sub.L (t,x.sub.L,y.sub.L).