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: Evaluating casing thickness by inducing SH0 and SH1 modes of a shear wave in the casing. The SH0 group velocity and SH1 mode group velocity (Vg) are measured and the measured SH0 mode group velocity is assigned as the tubular material shear velocity (Vs). A shear wave wavelength ? from the ratio of SH0 mode frequency (fo) and the measured SH0 group velocity is estimated. The tubular thickness (d) is estimated from the estimated shear wave wavelength ?. The transmitter can be calibrated to operate at an optimum frequency.

Abstract: Cross-dipole measurements are obtained in a borehole. By estimating a direction of polarization of the fast shear mode at low and high frequencies and comparing the estimated distances, a cause of anisotropy is established. Formation stresses and directions may be estimated.

Abstract: Stoneley-wave data acquired in the LWD environment are used to characterize/estimate formation permeability. Real-time Stoneley-wave time-delay/slowness and center-frequency/attenuation data are used to indicate/characterize formation permeability even during drilling. The use of stabilizers mounted at the tool ends helps maintain the tool position from severe decentralization, reducing ambiguities in the permeability characterization/estimation.

Abstract: A drilling system makes measurements of at least one drilling parameter such as downhole weight on bit, bit torque, bit revolutions, rate of penetration and bit axial acceleration, and at least one measurement responsive to formation properties. One or more processors use the measurements of drilling parameters and formation properties to adjust drilling parameters.

Abstract: Passive suppression of casing signals is used to improve the ability to measure formation velocities. Passive suppression includes the use of a magnet slidably coupled to the casing.

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: Measurements made by a transducer assembly for downhole imaging are affected by reverberations between the transducer and the window on the outside of the assembly. The reverberations result in a stationary noise on the image. Hardware solutions to improve signal-to-noise ratio includes using a composite transducer, adjusting the distance between the transducer and the window. SNR can also be improved by processing techniques that include stacking, fitting a sinusoid to the reverberation, by envelope peak detection, and by applying a notch filter.

Abstract: Evaluating casing thickness by inducing SH0 and SH1 modes of a shear wave in the casing. The SH0 group velocity and SH1 mode group velocity (Vg) are measured and the measured SH0 mode group velocity is assigned as the tubular material shear velocity (Vs). A shear wave wavelength ? from the ratio of SH0 mode frequency (fo) and the measured SH0 group velocity is estimated. The tubular thickness (d) is estimated from the estimated shear wave wavelength ? The transmitter can be calibrated to operate at an optimum frequency.

Abstract: Measurements of impedance are made using a piezoelectric transducer oriented at different angles to a formation bedding plane. The impedance measurements are then used to estimate the anisotropic velocity of the formation.

Abstract: A method and apparatus useful to determine the integrity of a cement bond log disposed in the annular space between a casing and a wellbore. The method and apparatus produce a transversely polarized shear wave and emit the wave through the casing and into the wellbore. The transversely polarized shear wave attenuates upon passage through the cement bond log. The integrity of the cement bond log can be determined through an analysis and evaluation of the attenuation results.

Abstract: An apparatus and method for providing a downhole acoustic source is disclosed. The acoustic source includes a piston configured to oscillate in an axial direction of the acoustic source and produce an acoustic signal in a medium in contact with an exterior surface of the piston, and an elastomer disposed on an interior side of the piston, an acoustic impedance of the elastomer selected to match an acoustic impedance of the piston. A permanent magnet is configured to provide a permanent magnetic field oriented in the axial direction, and a coil disposed on an interior side of the piston produces an alternating magnetic field in the region of the permanent magnetic field. The elastomer may be, for example, a silicon rubber, a silicone jelly, and a silicone oil. A plurality of acoustic sources may be arranged to produce an acoustic dipole configuration or an acoustic quadrupole configuration.

Abstract: Passive suppression of casing signals is used to improve the ability to measure formation velocities. Passive suppression includes the use of a magnet slidably coupled to the casing.

Abstract: A method for estimating a slowness of an earth formation, the method including: transmitting acoustic energy into the earth formation using an acoustic source; receiving the acoustic energy with an array of acoustic receivers, each acoustic receiver being configured to provide acoustic waveform data related to the received acoustic energy; transforming the acoustic waveform data into a frequency domain to provide frequency domain data; calculating a slowness-frequency coherence function using the frequency domain data; selecting slowness dispersion data from peaks of the slowness-frequency coherence function; fitting a curve to the slowness dispersion data; and estimating the slowness from the curve.

Abstract: A method useful for evaluating the presence and/or the quality of the cement bond of a downhole tubular. The method involves measuring radial resonance modes of the tubular, and comparing those measured values to the unbound tubular resonant values of a calibration ring. For a well bonded tubular, the measured radial resonance should be greater than that of the unbound tubular calibration ring. In regions where a fluid, such as water surrounds the outside of the tubular, or the cement is otherwise not bonded to the outer surface of the tubular, the measured response should be less than the calibrated response. The calibration ring should have the same diameter, wall thickness, and be made of the same material as the tubular.

Abstract: Dispersive array acoustic data are acquired. A histogram is determined from the semblance-frequency coherence of the data. The low frequency limit of the data is estimated by matching the statistics of the histogram to the statistics of a modeling function.

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

Abstract: Passive and active suppression of casing signals is used to improve the ability to measure formation velocities. Passive suppression includes the use of a magnet slidably coupled to the casing. Active suppression uses measurement of casing signals to control the output of an electromechanical acoustic transducer which cancels the propagating signal. Feedback control may be provided.

Abstract: A procedure to determine VSP-WD (Vertical Seismic Profiling—While Drilling) first breaks in absolute time is described. By combining a seismic surface source and firing complex seismic pattern unique in time (with a highly accurate surface—downhole time reference system), an automatic downhole procedure for first break detection on the downhole data, even under harsh conditions (low signal to noise ratio), is established. 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. 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: 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.