Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to record a plurality of acoustic waveforms corresponding to acoustic waves received at azimuthally orthogonal dipole receiver arrays surrounded by a geological formation, the waves being generated by azimuthally orthogonal transmitter arrays. Further activity may include analytically estimating a global minimum of a predefined objective function with respect to an azimuth angle at a point in an auxiliary parameter space associated with a set of auxiliary parameters, minimizing the objective function at the analytically estimated angle with respect to the auxiliary parameters, removing existing ambiguities associated with the fast and slow principal flexural wave axes, and determining at least one property of the geological formation based on the global minimum. Additional apparatus, systems, and methods are disclosed.

Abstract: A method is described for determining a shear wave velocity of a transversely isotropic region of an earth formation traversed by a wellbore with a non-zero relative dip angle between a longitudinal axis of the wellbore and an axis of symmetry of the TI region. A sonic tool is used to measure shear velocities in the TI region with polarizations orthogonal to the longitudinal axis of the wellbore. One of the shear velocities is identified as a quasi-shear velocity. A shear wave velocity is calculated, as a function of the quasi-shear velocity, for propagation in a direction along the axis of symmetry of the TI region. Where the orientation of the sonic tool is not known and the measured shear velocities comprises a fast shear velocity and a slow shear velocity, the method comprises identifying either the fast or the slow shear velocity as a quasi-shear mode.

Abstract: A downhole tool, having a central axis defined, may selectively include a sensor section including one or more arms connected to the tool body with an open/close mechanism. The open/close mechanism is configured to move in a radial direction with respect to the axis of the tool body. The tool also includes at least one sensor attached to the arm, and the tool may include at least one transmitter section on the tool. The transmitter is configured to transmit acoustic energy to a formation.

Abstract: A system and computer-implemented method for determining properties of a subsurface region of interest from seismic data include obtaining seismic data and an initial earth property model, forward modeling using the initial earth property model to create modeled seismic data, transforming the modeled and actual seismic data to create frequency domain modeled and actual seismic data including amplitude portion and phase portions, measuring the misfit between the frequency domain modeled and actual seismic data to produce frequency domain residual seismic data, performing phase unwrapping of certain observed frequency components of the frequency domain residual seismic data to create an unwrapped residual phase portion, and inverting the unwrapped residual phase portion to determine desired properties of the subsurface region of interest.

Abstract: Disclosed herein is a method of delineating a second wellbore from a first wellbore. The method includes, emitting acoustic waves from a tool in the first wellbore, receiving acoustic waves at the tool reflected from the second wellbore, and determining orientation and distance of at least a portion of the second wellbore relative to the tool.

Abstract: The present disclosure is related to apparatuses and methods measuring and processing a characteristic of subsurface earth formations penetrated by a borehole. More specifically this present disclosure relates to a method and apparatus for measuring and processing an acoustic characteristic such as formation shear wave velocity of subsurface sonic waves after these waves traverse earth formations adjoining a borehole or passing through a portion of the subsurface. The apparatus may include: a bottomhole assembly, a drill bit configured to generate an acoustic signal, at least two acoustic detectors, and a processor. The acoustic signal may include a specific multipole signal that may propagate through an earth formation along the borehole. The method may include use of the apparatus, including steps for estimating a shear velocity of the acoustic signal using signals from the at least two acoustic detectors.

Abstract: Methods of and apparatus to image one or more subsurface formation features are disclosed. An example method includes generating acoustic waves with a transmitter and receiving the acoustic waves and acoustic data contained therein at one or more receivers. The example method also includes extracting one or more S-S, P-S or S-P reflected waveform data from the acoustic data, estimating a dip of the one or more subsurface formation features, migrating the one or more S-S, P-S or S-P reflected waveform data with the estimated dip and mapping the migrated one or more S-S, P-S or S-P reflected waveform data. In addition, the example method includes identifying one or more permeable subsurface formation features using the mapped migrated one or more S-S, P-S or S-P reflected waveform data.

Abstract: Example methods, apparatus and articles of manufacture to determine anisotropy indicators for subterranean formations are disclosed. A disclosed example method includes computing a first shear slowness value from measured quadrupole waves, computing a second shear slowness value from measured Stoneley waves, and comparing the first and second shear slowness values to determine an anisotropy indicator representative of anisotropy of a subterranean formation.

Abstract: In response to at least one input criterion, one or more target positions in an acquisition domain are determined for processing of survey data, where the survey data is acquired by survey equipment in the acquisition domain having a first set of dimensions, and where the processing of the survey data is to be performed in a processing domain having a second set of dimensions different from the first set of dimensions.

Abstract: Methods and apparatus to filter acoustic waveforms in downhole environments are described. An example method involves receiving acoustic waveform data representing acoustic signals traversing at least a portion of a borehole adjacent a subterranean formation and performing a direct transform operation on the acoustic waveform data to generate wavelet map data. The wavelet map data comprises a time-frequency representation of the acoustic waveform data.

Abstract: Methods and related systems are described for measuring and analyzing refracted acoustic energy. A plurality of receivers mounted are on a downhole tool, and are arranged and adapted to receive refracted acoustic energy from a downhole formation. Measurements of refracted acoustic energy is analyzed such that information relating to an azimuthal direction relative to the downhole tool of an interface within the downhole formation can be estimated. The receivers can be mounted on a drill collar as part of a LWD tool and steering of the drilling trajectory can be based in part on the estimated formation information.

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: A logging system for measuring anisotrophic properties of the materials penetrated by a borehole. A downhole or “logging tool” element of the system comprises a source section that comprises either a unipole or a dipole acoustic source. The receiver section comprises a plurality of receiver stations disposed at different axial spacings from the acoustic source. Each receiver station comprises one or more acoustic receivers. The system requires that the source and receiver sections rotate synchronously as the logging tool is conveyed along the borehole. Receiver responses are measured in a plurality of azimuthal angle segments and processed as a function of rotation angle of the tool. The logging system can be embodied as a logging-while-drilling system, a measurement-while-drilling system, and a wireline system that synchronously rotates source and receiver sections. All embodiments require that the acoustic source operate at a relatively high frequency.

Abstract: Methods and apparatus for estimating borehole mud slownesses are disclosed. An example method includes estimating a borehole drilling fluid slowness value based on a tube wave modulus value, a tube-wave slowness value, and a drilling fluid density value. The borehole is associated with an anisotropic elastic medium.

Abstract: Methods and apparatus to determine slowness of drilling fluid in an annulus are described. An example method of determining slowness of drilling fluid in an annulus of a borehole in a formation includes obtaining a first slowness of the drilling fluid in the annulus and measuring with a downhole tool slownesses of the formation based on the first slowness. The example method also includes determining a first compressibility of the formation based on the slownesses of the formation and a first density of the formation and calculating a second density and a second compressibility of the drilling fluid in the annulus based on the first density and the first compressibility. The method also includes calculating a second slowness of the drilling fluid in the annulus based on the second density and the second compressibility.

Abstract: A method for thermoelastic logging in a borehole of a subterranean formation. The method includes generating, by a computer processor, a reference dispersion based on a borehole wave dispersion measurement of the borehole, wherein the reference dispersion represents far-field elastic properties in the subterranean formation, analyzing, by the computer processor, a difference between the reference dispersion and the borehole wave dispersion measurement based on a thermoelastic model of the subterranean formation to generate an analysis result, and determining, by the computer processor and based on the analysis result, a temperature dependent parameter of the subterranean formation.

Abstract: Methods and apparatus for waveform processing are disclosed. An example method includes representing waveform data using space time propagators in the Discrete Radon Transform Domain. The method also includes identifying signals within the represented waveform data using a Sparisty Penalized Transform.

Abstract: An acoustic logging while drilling tool includes a single unipole acoustic transmitter longitudinally and azimuthally spaced apart from a single linear array of unipole acoustic receivers. In certain preferred embodiments, the linear array of unipole receivers is azimuthally spaced apart from the unipole transmitter by about either 90 or 180 degrees. A bipole logging while drilling tool includes two unipole acoustic transmitters and two linear arrays of unipole acoustic receivers.

Abstract: Methods and apparatus to optimize parameters in a downhole environment are described. An example downhole tool includes a transmitter to transmit a signal into a subterranean formation and one or more receivers to receive at least a portion of the acoustic signal. The downhole tool also includes a processor configured to determine slownesses of different acoustic modes at a frequency of the signal received. Each of the slownesses is associated with a first parameter and a second parameter. The different acoustic modes have substantially different sensitivities to at least one of the first parameter or the second parameter. The processor to invert the determined slownesses of the different acoustic modes to determine an optimized value of the first parameter and an optimized value of the second parameter.

Abstract: Methods and apparatus for waveform processing are disclosed. An example method includes estimating a theoretical value of a first input parameter and setting a second input parameter to a known value. The known value is different than an actual value of the second input parameter. The method also includes identifying a frequency band using a processor that minimizes an effect of the second input parameter on a shear slowness inversion value.

Abstract: Cased-hole radial profiling of shear parameters from sonic measurements is disclosed.

Abstract: Methods and apparatus for determining slowness of wavefronts. An example apparatus includes one or more sources spaced from a receiver. The one or more sources are to transmit one or more signals and the receiver is to receive at least a portion of the one or more signals. The apparatus includes a processor to process waveform data associated with the one or more signals by stacking waveforms of the waveform data based on to linear moveout and sinusoidal moveout.

Abstract: Methods and apparatus for modeling formations are disclosed. An example apparatus includes a source spaced from receivers. The source is to transmit a signal and the receivers are to receive at least a portion of the signal. The example apparatus also includes a processor to process waveform data associated with the signal by generating a parameter estimate used in an inversion of Stoneley dispersion to enable a Stoneley shear slowness to substantially correspond to a slow-shear slowness when the apparatus is at least partially positioned in a horizontal wellbore of a vertical transverse isotropy formation.

Abstract: In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole.

Abstract: A methodology improves sampling and characterization of heterogeneous, unconventional hydrocarbon-bearing regions. The methodology is designed to integrate consistently across measurements and scales. Additionally, the methodology involves characterizing various scales, such as regional-scale heterogeneity, wellbore-scale heterogeneity, core-scale heterogeneity, sample-scale, and pore-scale heterogeneity. The results are integrated across the multiple scales based on results obtained from the characterization of the scales. The methodology further comprises determining data propagation across the multiple scales in a hydrocarbon-bearing region.

Abstract: In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole. The method includes generating within a borehole an intermittent low frequency vibration that propagates as a tube wave longitudinally to the borehole and induces a nonlinear response in one or more features in the material that are substantially perpendicular to a longitudinal axis of the borehole; generating within the borehole a sequence of high frequency pulses directed such that they travel longitudinally to the borehole within the surrounding material; and receiving, at one or more receivers positionable in the borehole, a signal that includes components from the low frequency vibration and the sequence of high frequency pulses during intermittent generation of the low frequency vibration, to investigate the material surrounding the borehole.

Abstract: A method for determining on a real time logging while drilling (LWD) basis gas within earth formations traversed by a borehole. Continuous LWD acoustic measurements are recorded and processed including coherent energy and attenuation attributes to detect downhole gas zones and kick during drilling operations.

Abstract: A method and apparatus for determining an effective cross-sectional area of a borehole including one or more sources for generating tube or Stoneley waves in the borehole; receivers for measuring amplitudes of the waves; and means to relate said measured amplitudes to said effective cross-sectional area or related parameters.

Abstract: A method is described for determining a shear wave velocity of a transversely isotropic region of an earth formation traversed by a wellbore with a non-zero relative dip angle between a longitudinal axis of the wellbore and an axis of symmetry of the TI region. A sonic tool is used to measure shear velocities in the TI region with polarisations orthogonal to the longitudinal axis of the wellbore. One of the shear velocities is identified as a quasi-shear velocity. A shear wave velocity is calculated, as a function of the quasi-shear velocity, for propagation in a direction along the axis of symmetry of the TI region. Where the orientation of the sonic tool is not known and the measured shear velocities comprises a fast shear velocity and a slow shear velocity, the method comprises identifying either the fast or the slow shear velocity as a quasi-shear mode.

Abstract: Systems and methods for geological medium exploration are provided herein. A method of geological medium exploration may include generating vibrations in a geological medium and recording wave-fields at a surface and in a borehole. Additionally, the method may include obtaining a wave field modification operator and applying the wave-field operator to a full range of seismic data to achieve a spectrally-modified wave field.

Abstract: The invention discloses a way to recover separated seismograms with reduced interference noise by processing vibroseis data recorded (or computer simulated) with multiple vibrators shaking simultaneously or nearly simultaneously (200). A preliminary estimate of the separated seismograms is used to obtain improved seismograms (201). The preliminary estimate is convolved with the vibrator signature and then used to update the seismogram. Primary criteria for performing the update include fitting the field data and satisfying typical criteria of noise-free seismograms (202). Alternative ways to update are disclosed, including signal extraction, modeled noise extraction, constrained optimization based separation, and penalized least-squares based separation. The method is particularly suited for removing noise caused by separating the combined record into separate records for each vibrator, and is advantageous where the number of sweeps is fewer than the number of vibrators (200).

Abstract: A method and apparatus for determining an effective cross-sectional area of a borehole including one or more sources for generating tube or Stoneley waves in the borehole; receivers for measuring amplitudes of the waves; and means to relate said measured amplitudes to said effective cross-sectional area or related parameters.

Abstract: Method for separating different seismic energy modes in the acquisition (65) of seismic survey data by using sensors that preferentially record a single mode (63), optionally combined with a source that preferentially transmits that mode.

Abstract: The present invention refers to a method for determining the rigidity of a geological layer in terms of propagation velocity of the elastic waves within a geological system delimited by a free surface (2) and comprising at least one first geological layer (6) having a second rigidity and a second geological layer (5) having a second rigidity and being arranged below the first geological layer, said first and second layer being separated from each other by an interface (3), the method comprising the steps of: positioning a source (4) suitable to generate seismic waves in the second geological layer (5), whose rigidity is intended to be measured; activating said source of seismic waves; detecting at least one seismic signal by means of at least one sensor arranged coupling with the free surface, and determining—from at least one seismic signal—a shear velocity of the elastic waves in the second layer and thus indicating the rigidity of the second layer.

Abstract: A method for evaluating fractures induced in subsurface formations includes determining hypocenters and origin times of induced seismic events from seismic signals detected by seismic sensors deployed above a volume of the subsurface formations to be evaluated and recording the detected signals for a selected time. A modified Gutenberg-Richter exponent is determined for each induced seismic event having at least a selected number of other induced seismic events within a selected radial distance thereof. A spatial distribution of the modified Gutenberg-Richter exponents is used to determine at least one property of the induced fractures.

Abstract: A radial shear velocity profile of an earth formation is obtained by using dipole and/or cross-dipole measurements. The non-uniqueness in the inversion is addressed by using a constraint based on the fact that high-frequency dipole shear waves are mostly sensitive to the near-borehole shear velocity.

Abstract: A distributed acoustic wave detection system and method is provided. The system may include a fiber optic cable deployed in a well and configured to react to pressure changes resulting from a propagating acoustic wave and an optical source configured to launch interrogating pulses into the fiber optic cable. In addition, the system may include a receiver configured to detect coherent Rayleigh noise produced in response to the interrogating pulses. The CRN signal may be used to track the propagation of the acoustic waves in the well. Such capability allows the location of the cement sheath, as well as measuring the bonding of cement to at least a casing string at least partially surrounded by a cement sheath.

Abstract: An exemplary method for filtering multi-component seismic data is provided. One or more characteristics of the seismic data corresponding to a relative manifestation of surface wave noise on the different components, such as polarization attributes, are identified. A time-frequency boundary in the seismic data is also identified in the time-frequency transform domain, the time-frequency boundary delineating portions of the seismic data estimated to contain surface wave noise (302). Finally, filtered seismic data are created (306) by removing portions of the seismic data that correspond to the identified characteristics of surface waves and that are within the time-frequency boundary (303).

Abstract: A method for determining properties of a formation comprises disposing at least one acoustic logging tool in a well and moving the logging tool along the well. An acoustic logging is performed during movement of the acoustic logging tool together with simultaneous thermal treatment of the formation. A temperature of a formation zone being thermally treated is measured as well as attenuation and velocity of the Stoneley waves excited by the acoustic logging tool. Based on the obtained dependencies of measured parameters as functions of the formation zone temperature formation relative phase permeabilities, formation fluid viscosity and viscous flow activation energy are determined.

Abstract: Methods and apparatus to optimize parameters in a downhole environment are described. An example downhole tool includes a transmitter to transmit a signal into a subterranean formation and one or more receivers to receive at least a portion of the acoustic signal. The downhole tool also includes a processor configured to determine slownesses of different acoustic modes at a frequency of the signal received. Each of the slownesses is associated with a first parameter and a second parameter. The different acoustic modes have substantially different sensitivities to at least one of the first parameter or the second parameter. The processor to invert the determined slownesses of the different acoustic modes to determine an optimized value of the first parameter and an optimized value of the second parameter.

Abstract: In some aspects of the disclosure, a method for creating three-dimensional images of non-linear properties and the compressional to shear velocity ratio in a region remote from a borehole using a conveyed logging tool is disclosed.

Abstract: The invention discloses a way to recover separated seismograms with reduced interference noise by processing vibroseis data recorded (or computer simulated) with multiple vibrators shaking simultaneously or nearly simultaneously (200). A preliminary estimate of the separated seismograms is used to obtain improved seismograms (201). The preliminary estimate is convolved with the vibrator signature and then used to update the seismogram. Primary criteria for performing the update include fitting the field data and satisfying typical criteria of noise-free seismograms (202). Alternative ways to update are disclosed, including signal extraction, modeled noise extraction, constrained optimization based separation, and penalized least-squares based separation. The method is particularly suited for removing noise caused by separating the combined record into separate records for each vibrator, and is advantageous where the number of sweeps is fewer than the number of vibrators (200).

Abstract: A computer-implemented method of characterizing elastic properties of a subsurface formation at various fluid saturation conditions is disclosed.

Abstract: The present disclosure is related to methods and apparatuses for acoustic velocity well logging. The method may include estimating a magnitude of a principal horizontal stress in a borehole in a formation. The method may include obtaining a far field stress orientation and making a measurement of near borehole stress orientation. The present disclosure also includes an apparatus configured to be conveyed into a borehole and perform the method. Formation stresses and directions may be estimated.

Abstract: Methods and apparatus to filter acoustic waveforms in downhole environments are described. An example method involves receiving acoustic waveform data representing acoustic signals traversing at least a portion of a borehole adjacent a subterranean formation and performing a direct transform operation on the acoustic waveform data to generate wavelet map data. The wavelet map data comprises a time-frequency representation of the acoustic waveform data.

Abstract: A system and a method includes generating a first signal at a first frequency; and a second signal at a second frequency. Respective sources are positioned within the borehole and controllable such that the signals intersect in an intersection volume outside the borehole. A receiver detects a difference signal returning to the borehole generated by a non-linear mixing process within the intersection volume, and records the detected signal and stores the detected signal in a storage device and records measurement parameters including a position of the first acoustic source, a position of the second acoustic source, a position of the receiver, elevation angle and azimuth angle of the first acoustic signal and elevation angle and azimuth angle of the second acoustic signal.

Abstract: A system and method for investigating rock formations outside a borehole are provided. The method includes generating a first compressional acoustic wave at a first frequency by a first acoustic source; and generating a second compressional acoustic wave at a second frequency by a second acoustic source. The first and the second acoustic sources are arranged within a localized area of the borehole. The first and the second acoustic waves intersect in an intersection volume outside the borehole. The method further includes receiving a third shear acoustic wave at a third frequency, the third shear acoustic wave returning to the borehole due to a non-linear mixing process in a non-linear mixing zone within the intersection volume at a receiver arranged in the borehole. The third frequency is equal to a difference between the first frequency and the second frequency.

Abstract: A system and a method for generating a three-dimensional image of a rock formation, compressional velocity VP, shear velocity VS and velocity ratio VP/VS of a rock formation are provided. A first acoustic signal includes a first plurality of pulses. A second acoustic signal from a second source includes a second plurality of pulses. A detected signal returning to the borehole includes a signal generated by a non-linear mixing process from the first and second acoustic signals in a non-linear mixing zone within an intersection volume. The received signal is processed to extract the signal over noise and/or signals resulting from linear interaction and the three dimensional image of is generated.

Abstract: The present invention provides an improved method for estimating anisotropic formation from wave data using present-day logging tools that allow for the detection of compressional wave splitting to identify fracture direction. This methodology for analyzing compressional waveforms uses the Alford rotation method.

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.