Abstract: A cableless seismic acquisition system that is configured to resolve the locations of a plurality of cableless seismic acquisition units (e.g., up to 1,000,000 or more) of the system at sub-meter levels of accuracy (e.g., less than 10 cm, less than 5 cm, etc.) free of many of the limitations of existing manners of determining cableless unit locations in seismic acquisition systems. While accurately determining cableless unit locations for use in mapping underground structures of interest, the disclosed cableless seismic acquisition system also limits power demands of and ultimately power consumption by the cableless units to extend serviceable deployment time of the cableless acquisition system.

Abstract: Computer systems and methods are provided for time domain reconstructed seismic wavefield imaging. The original source signal or extended source can be forward propagated based on a model of a subsurface region, in order to generate a residual by comparison to field data. The residual can be back-propagated to generate a reconstructed source signal, which can be forward propagated to generate a reconstructed source wavefield. Seismic images can be generated by cross correlating the forward-propagated reconstructed source wavefield and the back-propagated receiver wavefield. The model can include seismic parameters such as velocity, density, anisotropy and attenuation characterizing the subsurface region, and can be iteratively refined to improve image quality, based on the reconstructed source wavefield in comparison to the field data.

Abstract: Systems and methods of optical link communication with seismic data acquisition units are provided. The systems and methods can perform at least portions of seismic data acquisition survey. A plurality of seismic data acquisition units can be deployed on a seabed. An optical communications link can be established between an extraction vehicle and at least one of the seismic data acquisition units. A frequency of the at least one seismic data acquisition unit can be syntonized or synchronized via the optical communications link. The at least one seismic data acquisition unit can be instructed to enter a low power state subsequent to syntonizing the frequency of the at least one seismic data acquisition unit. The seismic data acquisition unit can exit the low power state and acquire seismic data in an operational state.

Abstract: A method for processing microseismic data, comprises: receiving the microseismic data acquired by one or more multicomponent sensors; convolving the microseismic data with an operator that is applied to all of the components of the microseismic data; and applying a multicomponent filter operator to the convolved microseismic data. The microseismic data may result from human activity or be entirely natural. The filtering preserves the polarity of the received data while improving the signal-to-noise ratio of the filtered data.

Abstract: A method for use in seismic exploration comprises: accessing a set of seismic data representative of a subterranean geological formation and a subsurface attribute model of the subterranean geological formation; performing a wavefield extrapolation on the seismic data in the subsurface attribute model; applying the time-shift extended imaging condition to the extrapolated wavefields; forming shot-indexed, time shift gathers for each image pixel of the subsurface attribute model from the conditioned extrapolated wavefields; adaptively focusing the gathers; and stacking the adaptively focused gathers; and imaging the subterranean geological formation from the stacked, adaptively focused gathers. The method may, in some aspects, be realized by a computing apparatus programmed to perform the method or as a set of instructions encoded on a non-transitory program storage medium that, when executed by a computing apparatus, perform the method.

Abstract: The present invention relates generally to an apparatus and method for calculating efficient 3-dimensional (3D) traveltime by using coarse-grid mesh for a shallow depth source. More particularly, the present invention relates to an efficient 3D traveltime calculation method for a shallow depth source by combining a suppressed wave equation estimation of traveltime (SWEET) algorithm and an equivalent source distribution (ESD) algorithm, wherein the SWEET algorithm is a traveltime calculation algorithm using an damped wave equation and the ESD algorithm is for equivalently distributed sources; and to an apparatus and method for calculating efficient 3D traveltime by using coarse-grid mesh for a shallow depth source which may need less calculation time compared with that of a conventional SWEET algorithm.

Abstract: A sensor may determine a sampling pattern based on a group of synchronization signals received by the sensor. The sampling pattern may identify an expected time for receiving an upcoming synchronization signal. The sensor may trigger, based on the sampling pattern, a performance of a sensor operation associated with the upcoming synchronization signal. The performance of the sensor operation may be triggered before the upcoming synchronization signal is received.

Abstract: Method and device for generating an induced source shot point gather. The method includes receiving seismic data at least partially generated by an unintentional seismic source; calculating plural reconstructed receiver traces (RGi) based on pairing traces from the seismic data; and generating the induced source shot point gather based on the plural reconstructed receiver traces (RGi).

Abstract: Techniques for Gaussian beam migration imaging are described herein. According to some aspects, a seismic wave field of an earth surface is represented in the form of superposition of Gaussian beams with a present curvature parameter in a time-space domain. A width of the Gaussian beam based function and a spacing between centers of adjacent Gaussian beams of the seismic wave field of the earth surface are set as a preset width and spacing, respectively. A decomposition model is established according to the set seismic wave field. An optimization solution algorithm is applied, based on seismic data and a medium velocity model, to the decomposition model to obtain multiple waveform functions. Gaussian beams corresponding to the multiple waveform functions are propagated, based on the medium velocity model. Migration imaging is performed to obtain migration imaging results.

Abstract: Described herein is a land seismic data acquisition system comprising a central processing unit; a cabled network connected to the central processing unit comprising a plurality of acquisition lines each comprising: electronic units assembled in series along a telemetry cable and each associated with at least one seismic sensor, the units processing signals transmitted by the sensor(s); intermediate modules assembled in series along the telemetry cable and each associated with at least one of the electronic units, each intermediate module providing power supply and synchronization of the electronic unit(s) wherewith it is associated; wherein each electronic unit is associated with at least two intermediate modules including at least one upstream and at least one downstream from the electronic unit along the telemetry cable, and comprises synchronization means independent from the cabled network, bidirectional and autonomous power supply means, bidirectional storage means of the signals processed by the electr

Abstract: A method for seismic imaging of a subsurface volume of interest may include an imaging technique such as reverse time migration which uses a conditioned velocity model that replaces at least one sharp velocity transition with a gradual velocity transition including a velocity overshoot layer. The method may be performed by a computer system.

Abstract: A method for performing a hydrocarbon production action on an earth formation includes: obtaining a first vertical seismic profile (VSP) of the earth formation before a stimulation treatment is applied to the earth formation, the first VSP having first seismic data of a seismic property of received first seismic waves, and obtaining a second VSP of the earth formation after the stimulation treatment is applied to the earth formation, the second VSP comprising second seismic data of the seismic property of received second seismic waves. The method further includes quantifying a difference between the second seismic data and the first seismic data and performing the hydrocarbon production action using the quantified difference.

Abstract: A system and method for performing a target-oriented reverse time migration may include obtaining a seismic dataset and a geologic model representative of the subsurface volume of interest; identifying a target based on the seismic dataset and the geologic model; calculating a normal to represent a structural dip direction for at least one point on the target; upward propagating a cluster of beams from the at least one point on the target to a surface representing an acquisition surface of the seismic data; identifying valid source-receiver beam pairs based on coverage of the seismic dataset; accumulating coverage of the valid source-receiver beam pairs; identifying traces from the seismic dataset that fall within the accumulated beam pair coverage; and performing a target-oriented reverse time migration using the identified traces to produce a seismic image.

Abstract: In the present inventive method, individual traces of seismic data are migrated (41) without any assembling of different midpoints or any summing of different offsets, so that post-migration processing or analysis, e.g. trace alignment, may be applied to the individual migrated traces (42) to compensate for any deficiencies among them, before stack and assembly. Thus, the present invention fully separates the steps of migration (41), assembly (43), and stacking (44), which are combined together in traditional migration. Thus, imaging deficiencies can be measured and addressed in the image space before they are obscured by summation. Afterward, summation can proceed to construct the improved final image (45).

Abstract: Methods and systems for ghost compensation of seismic data in conjunction with Kirchhoff migration are described. Input traces are deghosted by applying a deghost operator thereto across a range of ray parameters, which ray parameters are associated with the Kirchhoff migration. The deghosted traces are buffered and then selected for use in the mapping stage of Kirchhoff migration.

Abstract: The method processes input including, for each of a plurality of shots at respective source locations, seismic traces recorded at a plurality of receiver locations. Offset-modulated data are also computed by multiplying the seismic data in each seismic trace by a horizontal offset between the source and receiver locations for said seismic trace. A depth migration process is applied to the seismic data to obtain a first set of migrated data, and to the offset-modulated data to obtain a second set of migrated data. For each shot, offset values are estimated and associated with respective subsurface positions, by a division process applied to the first and second sets of migrated data.

Abstract: The invention includes a method for reducing noise in migration of seismic data, particularly advantageous for imaging by simultaneous encoded source reverse-time migration (SS-RTM). One example embodiment includes the steps of obtaining a plurality of initial subsurface images; decomposing each of the initial subsurface images into components; identifying a set of components comprising one of (i) components having at least one substantially similar characteristic across the plurality of initial subsurface images, and (ii) components having substantially dissimilar characteristics across the plurality of initial subsurface images; and generating an enhanced subsurface image using the identified set of components. For SS-RTM, each of the initial subsurface images is generated by migrating several sources simultaneously using a unique random set of encoding functions. Another embodiment of the invention uses SS-RTM for velocity model building.

Abstract: A method for processing seismic data includes receiving seismic data and a velocity model (c(x)) for a plurality of locations (x), scaling a dimension of the seismic data according to the velocity model (c(x)) to provide a velocity normalized seismic data, and generating a final image (S(x)) of the subsurface using the velocity normalized seismic data. The velocity normalized seismic data may be a reverse-time migration image (I(x,?)) corresponding to the plurality of locations (x) and a plurality of propagation distance offsets (?). The method may also include transforming the reverse-time migration image (I(x,?)) for the plurality of selected positions (x) to a wavenumber domain to provide velocity normalized wavenumber data (I(k,?)) and suppressing data components corresponding to non-physical or undefined reflection angles to provide enhanced wavenumber data (I?(k,?)) and using the enhanced wavenumber data (I?(k,?)) to generate the final image (S(x)). A corresponding apparatus is also disclosed herein.

Abstract: Example computer-implemented method, computer-readable media, and computer system are described for generating subterranean imaging data based on vertical seismic profile (VSP) data. In some aspects, VSP data of a subterranean region can be received. Four angle attributes for each image point can be computed based on the received VSP data. Five-dimensional (5D) angle-domain common-image gathers (ADCIG) can be generated according to a ray-equation method based on the four angle attributes.

Abstract: Computing device and method for processing seismic traces to produce an image of a subsurface area. The method includes receiving a series of seismic traces related to the subsurface area and recorded by one or more seismic receivers, wherein the one or more seismic sources are originally generated by a source; applying a phase encoding function to the series of seismic traces, at least a portion of said seismic traces comprise signals reflected by geological interfaces of the subsurface area; applying a 3 dimensional (3D) harmonic-source reverse time migration of the series of seismic traces encoded with the phase encoding function; computing a forward wavefield by solving a first wave equation; computing a backward wavefield by solving a second wave equation; and cross-correlating the forward wavefield with the backward wavefield to generate an image of the subsurface.

Abstract: A method of developing a velocity model for processing a seismic dataset is implemented at a computer system having a processor and memory. The method includes: deriving a first velocity model from the seismic dataset; building a basin model based on the first velocity model and interpretation of the seismic dataset; validating the basin model using calibration data; deriving a second velocity model from the validated basin model; and updating the first velocity model based, at least in part, on the second velocity model.

Abstract: Computing systems and methods for improving imaging of collected data are disclosed. In one embodiment, a first wavefield is propagated to obtain a first wavefield history; the first wavefield is again propagated to obtain a second wavefield history, wherein the propagation includes integration of one or more Q-effects; a first attenuated traveltime history is estimated based at least in part on the first and second wavefield histories; a first Q-model filter is calculated based at least in part on the first estimated attenuated traveltime; and a first adjusted wavefield is generated based at least in part on application of the first Q-model filter to the first wavefield. In some embodiments, an image is generated based at least on a first adjusted wavefield and a second wavefield.

Abstract: A method for processing seismic data includes receiving seismic data and a velocity model (c(x)) for a plurality of locations (x), scaling a dimension of the seismic data according to the velocity model (c(x)) to provide a velocity normalized seismic data, and generating a final image (S(x)) of the subsurface using the velocity normalized seismic data. The velocity normalized seismic data may be a reverse-time migration image (I(x,?)) corresponding to the plurality of locations (x) and a plurality of propagation distance offsets (?). The method may also include transforming the reverse-time migration image (I(x,?)) for the plurality of selected positions (x) to a wavenumber domain to provide velocity normalized wavenumber data (I(k,?)) and suppressing data components corresponding to non-physical or undefined reflection angles to provide enhanced wavenumber data (I?(k,?)) and using the enhanced wavenumber data (I?(k,?)) to generate the final image (S(x)). A corresponding apparatus is also disclosed herein.

Abstract: Computing device and method for processing seismic traces to produce an image of a subsurface area. The method includes receiving a series of seismic traces related to the subsurface area and recorded by one or more seismic receivers, wherein the one or more seismic sources are originally generated by a source; applying a phase encoding function to the series of seismic traces, at least a portion of said seismic traces comprise signals reflected by geological interfaces of the subsurface area; applying a 3 dimensional (3D) harmonic-source reverse time migration of the series of seismic traces encoded with the phase encoding function; computing a forward wavefield by solving a first wave equation; computing a backward wavefield by solving a second wave equation; and cross-correlating the forward wavefield with the backward wavefield to generate an image of the subsurface.

Abstract: Seismic imaging systems and methods that employ sensitivity kernel-based migration velocity analysis in 3D anisotropic media may demonstrate increased stability and accuracy. Survey data analysts employing the disclosed systems and methods are expected to provide better images of the subsurface and be better able to identify reservoirs and deposits for commercial exploitation. Certain embodiments migrate seismic survey data with an anisotropic velocity model to obtain common angle image gathers. These gathers are processed to obtain depth residuals along one or more horizons. Angle-domain sensitivity kernels are used to convert the depth residuals into velocity errors, which are then used to refine the velocity model. A user is then able to view a representation of the subsurface structure determined in part from the refined velocity model. Multiple iterations may be needed for the velocity model to converge. The velocity model may be a layered to have constant velocity values between formation boundaries.

Abstract: Various technologies for a seismic acquisition system, which may include an acquisition central system configured to determine a desired start time for a sweep cycle in one or more vibrators and a recorder source system controller in communication with the acquisition central system. The recorder source system controller may be configured to receive the desired start time from the acquisition central system. The seismic acquisition system may further include one or more vibrator units in communication with the recorder source system controller. Each vibrator unit may be configured to start a sweep cycle in a vibrator at the desired start time.

Abstract: Blind wavelet extraction and de-convolution is performed on seismic data to enable its practical usage in seismic processing and to provide quality control of data obtained in areas where data from wells are not available. The wavelet extraction and deconvolution are realized in the time domain by iteration, producing a mixed phase wavelet with minimal prior knowledge of the actual nature of the wavelet. As a result of the processing, the de-convolved seismic reflectivity is obtained simultaneously.

Abstract: A computer-implemented method, system, and article of manufacture for generating images of a subsurface region are disclosed. The method includes obtaining seismic data and an earth model related to the subsurface region, forward propagating a source wavefield through the earth model for a limited time range dependent on a first travel time and a second travel time, backward propagating a receiver wavefield through the earth model for the limited time range dependent on the first travel time and the second travel time, and applying an imaging condition to the forward propagated source wavefield and backward propagated receiver wavefield to generate images related to the subsurface region. The first travel time is a length of time taken by seismic energy to travel from a seismic source to an image point in the subsurface region and the second travel time is a length of time taken by seismic energy to travel from a seismic receiver to the image point in the subsurface region.

Abstract: Method for estimating a model of seismic velocity in a subsurface region from seismic data (31) recorded on 3-component instruments. The method measures the apparent incidence angle (32) of a seismic wave observed at a surface as a function of wave frequency. This apparent angle is converted to an effective velocity as a function of frequency (33), which is then inverted (34) to obtain a subsurface velocity model.

Abstract: The invention relates to a method of seismic data processing, wherein the data includes a set of seismic traces, with each trace including a signal that has been recorded by a sensor after having been propagated in a subsurface area, with the signal being defined by an amplitude as a function of time, including the steps of: migration of data according to an initial time-velocity model, picking in the time-migrated data one or more event(s) corresponding to one or more subsurface reflector(s) so as to obtain facets locally approximating the event, kinematic demigration of the facets plotted so as to obtain simplified seismic data in the form of a set of facets and a set of attributes associated with the facets.

Abstract: A wireless seismic data acquisition unit with a wireless receiver providing access to a common remote time reference shared by a plurality of wireless seismic data acquisition units in a seismic system. The receiver is capable of replicating local version of remote time epoch to which a seismic sensor analog-to-digital converter is synchronized. The receiver is capable of replicating local version of remote common time reference for the purpose of time stamping local node events. The receiver is capable of being placed in a low power, non-operational state over periods of time during which the seismic data acquisition unit continues to record seismic data, thus conserving unit battery power. The system implements a method to correct the local time clock based on intermittent access to the common remote time reference. The method corrects the local time clock via a voltage controlled oscillator to account for environmentally induced timing errors.

Abstract: The present disclosure relates to determining the attenuation of an electromagnetic signal passing through a conductive material. An antenna is provided and placed in relatively close proximity to the conductive material. An alternating current is passed through the antenna and the impedance of the antenna is measured. The attenuation is determined using the measured impedance. A single frequency measurement may be made, or multiple measurements using different frequencies may be made. Grouped parameters based on properties of the material and the frequency of the current are used to relate the coil impedance to the attenuation. A current frequency for which the ratio of the antenna's resistive part of the impedance to the angular frequency of the current is substantially insensitive to at least one of the parameters is preferred.

Abstract: A method for adjusting an isotropic depth image based on a mis-tie volume is provided. The method generally includes obtaining an isotropic velocity volume for a geophysical volume, obtaining an isotropic depth image of the geophysical volume, obtaining time-depth pairs at downhole locations in the geophysical volume, generating mis-tie values based on the time-depth pairs and the isotropic velocity volume, assigning uncertainties to the mis-tie values, generating a smoothest mis-tie volume that satisfies a target goodness of fit with the mis-tie values. Adjustment of the isotropic depth image may be achieved based on the mis-tie volume or a calibration velocity obtained from the mis-tie volume.

Abstract: A technique includes determining a first difference between a time that a first network element of a seismic acquisition network receives a first frame pulse from a second network element of the seismic acquisition network and a time that the first network element transmits a second frame pulse to the second network element. The technique includes determining a second difference between a time that the second network element receives the second frame pulse and a time that the second network element transmits the first frame pulse. The technique includes determining a transmission delay between the first and second network elements based on the first and second time differences.

Abstract: Methods and systems for generating a stable reverse time demigration (RTDM) equation for predicting wave phenomena such as reflections, refractions and multiples are described. A coupling term is added to an RTDM equation and reflectivity associated with the coupling term is replaced with a pseudo-density function derived from a nonlinear equation. The resultant coupled and stabilized RTDM equation is then used to predict the desired wave phenomena based on the applied seismic image.

Abstract: This is a method of separating simultaneous sources that uses an inversion-type approach. Each source will preferably activated at a random time with respect to the others. These random delays tend to make the interference between sources incoherent while the reflections create coherent events within a series of shots. The shot separation is performed via a numerical inversion process that utilizes the sweeps for each shot, the start times of each shot, and the coherence of reflection events between nearby shots. Implementation of this method will allow seismic surveys to be acquired faster and cheaper.

Abstract: Presented are systems and methods for wireless data acquisition. The wireless data acquisition may involve synchronizing modules within a data acquisition array. The synchronized data acquisition array may be used to facilitate a seismic survey. Synchronization may be facilitated by receipt of a reference time event such that a clock is synchronized based on the reference time event.

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: Images relating to a subsurface region may be generated based at least in part on a backward propagated source wavefield and a receiver wavefield. A source wavefield may be propagated from an initial wavefield-state forward in time, from an initial time-state to a final time-state, through an earth model associated with the subsurface region. The backward propagated source wavefield may be determined by propagating the source wavefield backward in time, from the final time-state to the initial time-state, through the earth model to reconstruct the initial wavefield-state. The receiver wavefield may be propagated, from the final time-state, through the earth model. The earth model may include at least one boundary region that can be defined as having one or more of absorbing characteristics, boosting characteristics, randomly perturbed characteristics, and/or other characteristics. As such, wavefields may be dampened, amplified, randomly scattered, and/or otherwise altered at the at least one boundary region.

Abstract: The interferometric method of enhancing passive seismic events includes the step of cross-correlation (CC) of the trace recorded at a reference receiver location with the traces recorded at the rest of receiver locations. Next, the CC traces are aligned to zero timing by applying shifts that are calculated by searching for the position of the maximum CC trace value. Subsequently, the aligned CC traces are summed to produce a stacked CC trace that has a signal-to-noise ratio (SNR) better than the individual CC traces. Lastly, the stacked CC trace is convolved with each raw trace to put the MS event at the correct timing. Due to this process, the timing of the MS event on the i-th convolved trace, tccasci, will be equal to the timing of the MS event on the corresponding i-th raw trace, i.e., tccasci=ti.

Abstract: This is a method of separating simultaneous sources that uses an inversion-type approach. Each source will preferably activated at a random time with respect to the others. These random delays tend to make the interference between sources incoherent while the reflections create coherent events within a series of shots. The shot separation is performed via a numerical inversion process that utilizes the sweeps for each shot, the start times of each shot, and the coherence of reflection events between nearby shots. This method will allow seismic surveys to be acquired faster and cheaper.

Abstract: A computer-implemented method, system, and article of manufacture for generating images of a subsurface region are disclosed. The method includes obtaining seismic data and an earth model related to the subsurface region, forward propagating a source wavefield through the earth model for a limited time range dependent on a first travel time and a second travel time, backward propagating a receiver wavefield through the earth model for the limited time range dependent on the first travel time and the second travel time, and applying an imaging condition to the forward propagated source wavefield and backward propagated receiver wavefield to generate images related to the subsurface region. The first travel time is a length of time taken by seismic energy to travel from a seismic source to an image point in the subsurface region and the second travel time is a length of time taken by seismic energy to travel from a seismic receiver to the image point in the subsurface region.

Abstract: Presented are systems and methods for wireless data acquisition. The wireless data acquisition may involve synchronizing modules within a data acquisition array. The synchronized data acquisition array may be used to facilitate a seismic survey. Synchronization may be facilitated by receipt of a reference time event such that a clock is synchronized based on the reference time event.

Abstract: A method of imaging the Earth's subsurface using passive seismic interferometry tomography includes detecting seismic signals from within the Earth's subsurface over a time period using an array of seismic sensors, the seismic signals being generated by seismic events within the Earth's subsurface. The method further includes adaptively velocity filtering the detected signals. The method further includes cross-correlating the velocity filtered seismic signals to obtain a reflectivity series at a position of each of the seismic 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: A method for spectrally conditioning surface seismic data. In one implementation, the method may include correcting surface seismic data for distortions due to anomalous spectral amplitudes, thereby generating a first set of corrected data; correcting the first set of corrected data for deterministic distortions, thereby generating a second set of corrected data; correcting the second set of corrected data for spectral distortions due to the seismic waves traveling through the near-surface, thereby generating a third set of corrected data; and correcting the third set of corrected data for spectral distortions due to the seismic waves traveling through deeper strata.

Abstract: Provided is seismic imaging, particularly, reverse-time migration for generating a real subsurface image from modeling parameters calculated by waveform inversion, etc. A frequency-domain reverse-time migration apparatus includes: a source estimator configured to estimate sources from data measured on a plurality of receivers; and a migration unit configured to receive information about the sources estimated by the source estimator and to perform reverse-time migration in the frequency domain. The source estimator estimates the sources by updating an initial source vector using incremental changes according to a full Newton method.

Abstract: Provided is seismic imaging, particularly, a time-domain reverse-time migration technique for generating a real subsurface image from modeling parameters calculated through waveform inversion, etc. A reverse-time migration apparatus according to an example includes a source estimator configured to estimate sources by obtaining transmission waveforms from data measured by a plurality of receivers, through waveform inversion, and a migration unit configured to receive information about the estimated sources, and to perform reverse-time migration in the time domain. The source estimator estimates sources, by solving first-order matrix equation including a Toeplitz matrix composed of autocorrelation values of the Green's function, and a cross-correlation matrix of measured data and the Green's function, through Levinson Recursion.

Abstract: A method for determining positions and origin times of seismic events occurring in the Earth's subsurface includes accepting as input to the method signals recorded from a plurality of seismic sensors deployed above a subsurface volume of interest. The recorded signals are a representation of seismic amplitude with respect to time. Origin time and location of each of a plurality of subsurface seismic events are determined from the recorded signals. The origin times and locations of each event are inverted to obtain Thomsen's parameters in formations in the volume of interest. Depths of each of the events are determined by individually searching the depth of each event, the inversion with each incorporated new depth including updating the Thomsen parameters and setting as a limit a minimum value of RMS error.

Abstract: Multipole acoustic logging-while-drilling (LWD) tools and associated methods are disclosed herein. In some embodiments, the disclosed acoustic LWD tool comprises a transmitter array and at least one receiver array. The transmitter array generates acoustic waves with an excitation pattern having a cutoff frequency greater than about 3 kHz. The receiver array is spaced apart from the transmitter array and is configured to detect said acoustic waves. Some of the disclosed method embodiments comprise: generating multipole acoustic waves in a fluid-filled borehole using an excitation pattern with a cutoff frequency greater than about 3 kHz; selectively detecting acoustic waves that propagate with said excitation pattern; and determining an acoustic shear wave slowness for a formation penetrated by the borehole.