Abstract: A method and apparatus for generating an acoustic signal having a single mode of propagation along borehole walls. The method includes generating an n-pole (monopole, dipole, quadrupole, and so on) acoustic signal and calculating the tool position and borehole shape from the signals received at one or more receivers. If the tool contains matched sources and balanced receivers, is in the center of the borehole, and the borehole is circular, the pure, single mode acoustic signal will propagate along the borehole walls with a single mode of propagation. If the acoustic signal traveling along borehole walls does not have a single mode of propagation, the signal's amplitudes and time delays are adjusted to produce a second acoustic signal. The second acoustic signal's amplitudes and time delays are further adjusted until the signal traveling along the borehole walls has a single mode of propagation.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may include generating attenuation values associated with a set of multiple signals received by multiple receivers from a transmitted signal as a function of reception time and material velocity. The attenuation values may be stored in a memory and/or displayed on a display, perhaps in conjunction with a semblance map.

Abstract: An acoustic caliper and a calipering method having reduced or eliminated blind spots. In one embodiment, the acoustic caliper comprises an array of two or more transducers that can detect acoustic pulses transmitted by other transducers in the array. One method embodiment comprises: transmitting an acoustic pulse from a selected transducer in a transducer array; configuring the array to listen for a reflection of the acoustic pulse; and determining a travel time for the acoustic pulse if a reflection is detected by at least one transducer in the array.

Abstract: Tools and methods are provided that determine the acoustic impedance of drilling fluid using reflections from a precise metal disk. Because the reverberation characteristics of an acoustic wave depend in part on the acoustic wave shape, the first reflection from the metal disk may be used to calibrate the measurement. A method for determining a borehole fluid property includes (i) generating an acoustic signal within a borehole fluid, (ii) receiving reflections of the acoustic signal from the fluid, and (iii) analyzing a reverberation portion of the acoustic signal to determine the property. The analyzing of the reverberation portion may include obtaining a theoretical reverberation signal and relating the measured reverberation signal with the theoretical reverberation signal to determine the borehole fluid property.

Abstract: A system and method is provided for characterizing earth formations. In one embodiment, the method includes passing a logging tool through a borehole and repeatedly: (a) triggering an acoustic wave generator; (b) recording acoustic waveforms received by receivers in the logging tool; (c) determining a time semblance of the recorded acoustic waveforms; and (d) smoothing the time semblance. In a different embodiment, a phase semblance of the recorded acoustic waveforms is determined and smoothed. The smoothing may be performed using an adaptive wavelet denoising technique or an adaptive moving average filter technique. In each case the average time or frequency spacing between semblance peaks is preferably determined and used to adapt the smoothing operation in a manner that varies with the slowness value s.

Abstract: A system and method is provided for characterizing earth formations. In one embodiment, the method includes passing a logging tool through a borehole and repeatedly: (a) triggering an acoustic wave generator; (b) recording acoustic waveforms received by receivers in the logging tool; (c) determining a time semblance of the recorded acoustic waveforms; and (d) smoothing the time semblance. In a different embodiment, a phase semblance of the recorded acoustic waveforms is determined and smoothed. The smoothing may be performed using an adaptive wavelet denoising technique or an adaptive moving average filter technique. In each case the average time or frequency spacing between semblance peaks is preferably determined and used to adapt the smoothing operation in a manner that varies with the slowness value s.

Abstract: A system and method is provided for characterizing earth formations. In one embodiment, the method includes passing a logging tool through a borehole and repeatedly: (a) triggering an acoustic wave generator; (b) recording acoustic waveforms received by receivers in the logging tool; (c) determining a time semblance of the recorded acoustic waveforms; and (d) smoothing the time semblance. In a different embodiment, a phase semblance of the recorded acoustic waveforms is determined and smoothed. The smoothing may be performed using an adaptive wavelet denoising technique or an adaptive moving average filter technique. In each case the average time or frequency spacing between semblance peaks is preferably determined and used to adapt the smoothing operation in a manner that varies with the slowness value s.

Abstract: The present invention finds the acoustic impedance of the drilling fluid using reflections from a precise metal disk, and therefrom the density of the drilling fluid. Because the reverberation characteristics of an acoustic wave depend in part on the acoustic wave shape, the first reflection from the metal disk may be used to calibrate the measurement. A method for determining a borehole fluid property is disclosed that includes (i) generating an acoustic signal within a borehole fluid, (ii) receiving reflections of the acoustic signal from the fluid, and (iii) analyzing a reverberation portion of the acoustic signal to determine the property. The analyzing of the reverberation portion may include obtaining a theoretical reverberation signal and relating the measured reverberation signal with the theoretical reverberation signal to determine the borehole fluid property.

Abstract: A system and method is provided for characterizing earth formations. In one embodiment, the method includes passing a logging tool through a borehole and repeatedly: (a) triggering an acoustic wave generator; (b) recording acoustic waveforms received by receivers in the logging tool; (c) determining a time semblance of the recorded acoustic waveforms; and (d) smoothing the time semblance. In a different embodiment, a phase semblance of the recorded acoustic waveforms is determined and smoothed. The smoothing may be performed using an adaptive wavelet denoising technique or an adaptive moving average filter technique. In each case the average time or frequency spacing between semblance peaks is preferably determined and used to adapt the smoothing operation in a manner that varies with the slowness value s.

Abstract: The acoustic impedance of the drilling fluid may be found using reflections from a precise metal disk, and therefrom the density of the drilling fluid. Because the reverberation characteristics of an acoustic wave depend in part on the acoustic wave shape, the first reflection from the metal disk may be used to calibrate the measurement. A method for determining a borehole fluid property is disclosed that includes (i) generating an acoustic signal within a borehole fluid, (ii) receiving reflections of the acoustic signal from the fluid, and (iii) analyzing a reverberation portion of the acoustic signal to determine the property. The analyzing of the reverberation portion may include obtaining a theoretical reverberation signal and relating the measured reverberation signal with the theoretical reverberation signal to determine the borehole fluid property.

Abstract: A system for obtaining video data is provided, the system comprising a video camera positioned down a bore-hole to obtain a plurality of video frames wherein the plurality of video frames comprises sequential video frames, wherein each of the sequential video frames contains information, and wherein a portion of the information of each of the sequential video frames comprises new information not found on a previous sequential video frame. The system also comprises a data extractor to extract information only from the portion comprising the new information from each sequential video frame.

Abstract: An acoustic tool that provides a programmable source waveform is disclosed. Numerous advantages may be achieved from the configurability of the source waveform. Notably, acoustic logs at multiple frequencies may be acquired with a single pass. The waveform may be frequency-adapted to maximize formation response and amplitude adapted for gain control. In one embodiment, the acoustic tool comprises: a controller, a digital-to-analog controller (DAC), an acoustic transducer, and a linear driver. The DAC converts a digital waveform from the controller into an analog waveform. The acoustic transducer converts an electrical signal into an acoustic signal. The linear driver receives the analog waveform from the DAC and responsively provides the electrical signal to the acoustic transducer. The electrical signal is proportional to the analog waveform. The tool may further include a memory for storing the digital waveform and/or software for generating the digital waveform.

Abstract: An acoustic tool that provides a programmable source waveform is disclosed. Numerous advantages may be achieved from the configurability of the source waveform. Notably, acoustic logs at multiple frequencies may be acquired with a single pass. The waveform may be frequency-adapted to maximize formation response and amplitude adapted for gain control. In one embodiment, the acoustic tool comprises: a controller, a digital-to-analog controller (DAC), an acoustic transducer, and a linear driver. The DAC converts a digital waveform from the controller into an analog waveform. The acoustic transducer converts an electrical signal into an acoustic signal. The linear driver receives the analog waveform from the DAC and responsively provides the electrical signal to the acoustic transducer. The electrical signal is proportional to the analog waveform. The tool may further include a memory for storing the digital waveform and/or software for generating the digital waveform.

Abstract: The present invention finds the acoustic impedance of the drilling fluid using reflections from a precise metal disk, and therefrom the density of the drilling fluid. Because the reverberation characteristics of an acoustic wave depend in part on the acoustic wave shape, the first reflection from the metal disk may be used to calibrate the measurement. A method for determining a borehole fluid property is disclosed that includes (i) generating an acoustic signal within a borehole fluid, (ii) receiving reflections of the acoustic signal from the fluid, and (iii) analyzing a reverberation portion of the acoustic signal to determine the property. The analyzing of the reverberation portion may include obtaining a theoretical reverberation signal and relating the measured reverberation signal with the theoretical reverberation signal to determine the borehole fluid property.

Abstract: An acoustic tool that provides a reduced tool mode and enhanced accuracy for estimating shear wave propagation slowness in slow formations is disclosed. In one embodiment, the acoustic tool comprises: an acoustic source, an array of acoustic receivers, and an internal controller. The acoustic source excites waves that propagate in a quadrapole mode. The internal controller processes signals from the array of acoustic receivers to determine a peak phase semblance having a slowness value that varies with frequency. The minimum slowness value associated with the peak phase semblance provides an accurate estimate of the shear wave propagation slowness. The acoustic source preferably includes four source elements. The elements that are 90° apart are preferably driven in inverse-phase to obtain the quadrapole excitation pattern.

Abstract: A system and method is provided for characterizing earth formations. In one embodiment, the method includes passing a logging tool through a borehole and repeatedly: (a) triggering an acoustic wave generator; (b) recording acoustic waveforms received by receivers in the logging tool; (c) determining a time semblance of the recorded acoustic waveforms; and (d) smoothing the time semblance. In a different embodiment, a phase semblance of the recorded acoustic waveforms is determined and smoothed. The smoothing may be performed using an adaptive wavelet denoising technique or an adaptive moving average filter technique. In each case the average time or frequency spacing between semblance peaks is preferably determined and used to adapt the smoothing operation in a manner that varies with the slowness value s.

Abstract: An apparatus and method for determining fast and slow shear wave velocities and orientations in an anisotropic earth formation that reduces the error and ambiguity in calculating these parameters and eliminates the need for dipole receivers and multiple dipole sources. The apparatus generally includes a single dipole source capable of generating an acoustic signal within a borehole. The acoustic logging tool contains multiple levels of receivers. At each level, four receivers, which may be conventional pressure transducers, receive shear/flexural wave signals which propagate along the borehole earth formation. These receivers measure the pressure fields from the wave signals. A processing device, preferably a UNIX™ based computer, interpolates the measured pressure fields between any two adjacent receivers. The processing device performs cross-component decomposition on the pressure field to determine shear wave orientation and velocity.

Abstract: A transducer configuration for use in acoustically imaging a target region behind an acoustically reflective layer includes a sonde having a geometrical center and constructed and arranged to support a plurality of transducers. The system includes a first transducer disposed within the sonde at a first distance from the geometrical center for generating a first acoustic pulse and for receiving a first acoustic signal. The acoustic signal comprises a first reflection from the reflective surface, a first set of fluid multiples arising from reflections between the reflective layer and a surface of the first transducer, and a first signal associated with the target area. The system also includes a second transducer disposed within the sonde at a second distance from the geometrical center for generating a second acoustic pulse and for receiving a second acoustic signal.

Abstract: A sonic or acoustic tool is disclosed which includes a transmitter with reduced transmitter spawned noise. The transmitters are either monopole or dipole depending on the orientation of ports in a chamber divided by a piston driven by an actuator. The transmitter size is limited only by the diameter of the tools itself because the transmitters are oriented within the tool parallel to the axis of the tool.

Abstract: A method and device are disclosed for determining the impedance of the cement bond between a borehole casing and its wellbore. The invention uses a predicted resonance response as a baseline for determining from the observed resonance response the approximate impedance of the cement. Corrections are made to account for various defects in the casing by normalizing the received resonance response.