Abstract: Methods for determining properties of a media on an exterior of a casing in downhole systems are described. The methods include conveying a logging tool through a casing in a downhole formation, stimulating shear waves and flexural waves in the casing, obtaining a shear attenuation rate measurement and a flexural attenuation rate measurement within the casing responsive to the media on the exterior of the casing, comparing the measured shear attenuation rate and the measured flexural attenuation rate against a plurality of respective division boundary values, and determining one or more properties of the media on the exterior of the casing based on the comparison of the measured shear attenuation rate and the measured flexural attenuation rate against the plurality of respective interfaces.

Abstract: A method for characterizing a tubular includes obtaining acoustic waveform data in a time domain using an acoustic transducer configured to emit an acoustic signal and receive a return acoustic signal and transforming the acoustic waveform data into a frequency domain to provide frequency domain acoustic waveform data. The method also includes determining a complex group delay function Gk derived from the frequency domain acoustic waveform data to provide a phase delay function as a function of frequency, wherein the complex group delay function Gk represents a first derivative of phase in the frequency domain with respect to frequency. The method further includes determining an imaginary component function of the complex group delay function Gk to provide a phase delay function as a function of frequency and characterizing the tubular using the phase delay function.

Abstract: A method for characterizing a tubular includes obtaining acoustic waveform data in a time domain using an acoustic transducer configured to emit an acoustic signal and receive a return acoustic signal and transforming the acoustic waveform data into a frequency domain to provide frequency domain acoustic waveform data. The method also includes determining a complex group delay function Gk derived from the frequency domain acoustic waveform data to provide a phase delay function as a function of frequency, wherein the complex group delay function Gk represents a first derivative of phase in the frequency domain with respect to frequency. The method further includes determining an imaginary component function of the complex group delay function Gk to provide a phase delay function as a function of frequency and characterizing the tubular using the phase delay function.

Abstract: Methods for determining properties of a media on an exterior of a casing in downhole systems are described. The methods include conveying a logging tool through a casing in a downhole formation, stimulating shear waves and flexural waves in the casing, obtaining a shear attenuation rate measurement and a flexural attenuation rate measurement within the casing responsive to the media on the exterior of the casing, comparing the measured shear attenuation rate and the measured flexural attenuation rate against a plurality of respective division boundary values, and determining one or more properties of the media on the exterior of the casing based on the comparison of the measured shear attenuation rate and the measured flexural attenuation rate against the plurality of respective interfaces.

Abstract: A method for characterizing a tubular includes obtaining acoustic waveform data in a time domain using an acoustic transducer configured to emit an acoustic signal and receive a return acoustic signal and transforming the acoustic waveform data into a frequency domain to provide frequency domain acoustic waveform data. The method also includes determining a complex group delay function Gk derived from the frequency domain acoustic waveform data to provide a phase delay function as a function of frequency, wherein the complex group delay function Gk represents a first derivative of phase in the frequency domain with respect to frequency. The method further includes determining an imaginary component function of the complex group delay function Gk to provide a phase delay function as a function of frequency and characterizing the tubular using the phase delay function.

Abstract: A system method and computer-readable medium for correcting measurements obtained by a down hole tool for residual measurement errors is disclosed. A down hole tool having at least two directional field sensors is disposed in a borehole. The at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool. Measurements are obtained from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool. Residual measurement errors are determined for the obtained measurements, and a quality level of the determined residual measurement errors selected. The determined residual measurement errors are applied to the obtained measurements when the determined residual measurement errors are consistent with the selected quality level.

Abstract: A system method and computer-readable medium for correcting measurements obtained by a down hole tool for residual measurement errors is disclosed. A down hole tool having at least two directional field sensors is disposed in a borehole. The at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool. Measurements are obtained from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool. Residual measurement errors are determined for the obtained measurements, and a quality level of the determined residual measurement errors selected. The determined residual measurement errors are applied to the obtained measurements when the determined residual measurement errors are consistent with the selected quality level.

Abstract: A method and apparatus for estimating a change in length of a wellbore conveyance device in a wellbore. A reference signal is sent along a first path and a wellbore signal having a phase relationship with the reference signal is sent along a wellbore path. A change in length of the wellbore conveyance device is estimated from a phase shift between the reference signal and the wellbore signal. The frequency of the wellbore signal may be changed downhole. The wellbore conveyance device may have at least one conductor under a maintained tension. A length of the wellbore conveyance device is estimated from the estimated change in the length. For a drill string composed of a plurality of wellbore tubulars, a phase shift of the drill sting is determined upon adding a wellbore tubular to the drill string.

Abstract: A method and apparatus for estimating a change in length of a wellbore conveyance device in a wellbore. A reference signal is sent along a first path and a wellbore signal having a phase relationship with the reference signal is sent along a wellbore path. A change in length of the wellbore conveyance device is estimated from a phase shift between the reference signal and the wellbore signal. The frequency of the wellbore signal may be changed downhole. The wellbore conveyance device may have at least one conductor under a maintained tension. A length of the wellbore conveyance device is estimated from the estimated change in the length. For a drill string composed of a plurality of wellbore tubulars, a phase shift of the drill sting is determined upon adding a wellbore tubular to the drill string.

Abstract: A method for calculating the orientation of a geologic feature with respect to the axis of a wellbore drilled through earth formations. The method uses finely detailed measurements of a selected property of the earth formations made along the wall of the wellbore. The method includes the steps of segregating the finely detailed measurements by an angle subtended with respect to an arbitrary reference on the circumference of the wellbore. The measurements are further segregated into a selected axial interval along the wellbore. For each segment, for each subtended angle, the segregated measurements are spectrally analyzed with respect to spatial frequency. Coefficients of a best fit curve are determined for the phase components of the spectrally analyzed measurements with respect to the subtended angle. The orientation of the geologic feature is calculated from the best fit curve.

Abstract: A fiber optic rotation sensor includes a 3.times.3 optical coupler formed of first, second and third optical waveguides. The first, second and third optical waveguides are formed such that the fractions of light coupled from any one of the first, second and third optical waveguides to the other two optical waveguides are constant, independent of thermally-induced changes in the interaction length. An optical signal source provides an input optical signal to the first optical waveguide such that portions of the input optical signal are coupled from the first optical waveguide into the second and third optical waveguides. The optical fiber in which the sensing loop is formed has ends that are coupled to the second and third optical waveguides to receive optical signals that form counterpropagating optical waves in a fiber optic sensing loop and to combine the counterpropagating optical waves after they have traversed the sensing loop.

Abstract: A method for using geometrical data to determine characteristics of a wellbore penetrating a subterranean formation is disclosed. The method involves converting data obtained from acoustic well logging into cartesian coordinates and solving a general quadratic equation by a least squares fit to an elliptical or circular model. More specific information, such as tensor strain and formation compaction along the wellbore may then be obtained from the geometrical data.

Abstract: A method for logging a subterranean formation from within a well that has been cased and cemented is disclosed. An acoustic signal is transmitted into the formation from a pulse-echo transducer placed within the wellbore and the first casing echo and the first formation echo are detected. The amplitude and the arrival times of these two echoes, combined with some known information about the wellbore, the casing, and the cement enable several parameters to be calculated. These parameters in turn may be used to image the formation around the well.

Abstract: This invention describes a methodology to image features using an array of multiple piezo-electric elements which employs the selective use of mechanical and electronic beam focusing, electronic beam steering and amplitude shading to increase resolution and overcome side lobe effects. This invention introduces a novel signal reconstruction technique utilizing independent array element transmission and reception, creating focusing and beam steering. Application of the methodology can be used in wireline, measurement while drilling, pipe and pipeline and medical applications. Applications include, but are not limited to Bore hole Caliper, Bore hole Geometry, Bore hole Imaging, Casing Inspection, Cement Evaluation and Volumetric Scanning Applications (e.g. Fluid, Behind Casing and Open Hole). The configuration of the transducer array is preferably cylindrical, but may be conical, biconical, convex, concave or may take the form of a number of suitable geometric configurations.

Abstract: A method for using geometrical data to determine characteristics of a wellbore penetrating a subterranean formation is disclosed. The method involves converting data obtained form acoustic well logging into cartesian coordinates and solving a general quadratic equation by a least squares fit to an elliptical or circular model. More specific information, such as tensor strain and formation compaction along the wellbore may then be obtained from the geometrical data.

Abstract: Signals indicative of the Sagnac phase shift between counterpropagating waves in a sensing loop are combined to produce an error signal. A phase modulator is arranged to modulate the phase of optical signals that pass through the sensing loop. A phase modulator driver apparatus responsive to the error signal produces a ramp signal to drive the phase modulator to null the error signal. A reset apparatus is arranged for resetting the ramp signal to when the phase reaches a predetermined limit. The reset apparatus preferably includes a reset integrator circuit arranged to produce an output that is a ramp signal whose slope is proportional to the rotation rate of the sensing loop. A pair of comparators is arranged to determine when the reset integrator reaches one of two rollover limits. Rollover logic circuitry is connected to the pair of comparators and arranged such that when the reset integrator reaches one of the rollover limits, the integrator is forced to the other integration limit.

Abstract: The signal-to-noise ratio of televiewer signals from a rotary sidewall acoustic-beam scanner is improved by replacing the volume of borehole drill fluid that lies in the path of the acoustic beam with a solid medium characterized by a lower coefficient of attenuation than that of the drill fluid.

Abstract: The present invention is a system for determining the depth of a logging tool attached to a cable extended into a wellbore penetrating an earth formation. In a preferred embodiment, the system includes a circuit for generating a measurement of phase shift in a sinusoidal electrical signal traversing the cable, the phase shift corresponding to a length of the cable. The system also comprises an accelerometer disposed within the tool and electrically connected to a bandpass filter and thence to a double integrator connected to the bandpass filter. The integrator calculates displacement of the tool coaxial with the wellbore. The phase shift measurement is filtered in a low pass filter. The low pass filter and the bandpass filter comprise at least some amount of bandpass overlap. The integrator output is used to generate a scale factor, which is applied to the filtered phase shift signal. The scaled phase shift signal is combined in a computer with a signal generated by a depth encoder.

Abstract: The invention is a method of determining the thickness of a casing in a wellbore penetrating an earth formation using group delay determined casing resonance extracted from processed reflection signals from an acoustic pulse-echo imaging tool. A first Fourier transform coefficient series is calculated from the digitized reflection signal. Individual samples of the reflection signal are multiplied by their sample index values to obtain a modified digitized data string. A second Fourier transform coefficient series is calculated from the modified digitized data. The complex group delay function is calculated directly from the first and second Fourier coefficient series.

Abstract: A fiber optic rotation sensor includes a [3.times.3] optical coupler formed of first, second and third optical waveguides. The first, second and third optical waveguides are formed such that the fractions of light coupled from any one of the first, second and third optical waveguides to the other two optical waveguides are constant, independent of thermally-induced changes in the interaction length. An optical signal source provides an input optical signal to the first optical waveguide such that portions of the input optical signal are coupled from the first optical waveguide into the second and third optical waveguides. The optical fiber in which the sensing loop is formed has ends that are coupled to the second and third optical waveguides to receive optical signals that form counterpropagating optical waves in a fiber optic sensing loop and to combine the counterpropagating optical waves after they have traversed the sensing loop.