Quadrupole acoustic shear wave logging while drilling
First Claim
1. A tool for generating signals indicative of shear wave slowness of the formation surrounding a borehole containing a fluid and a drill string, the tool adapted for use with a drill string having a plurality of drill collars jointed together, the tool comprising:
- a collar portion defining an axis and adapted for mounting in a drill string;
a quadrupole sonic transmitter mounted to the collar portion at a first location; and
a quadrupole sonic receiver array mounted to the collar portion at a second location, the second location spaced apart from the first location.
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Accused Products
Abstract
A tool generates signals indicative of shear wave slowness of the formation surrounding a borehole. The tool comprises a collar portion adapted for mounting in a drill string, a quadrupole sonic transmitter mounted to the collar portion, and a quadrupole sonic receiver array mounted to the collar spaced apart from the transmitter.
A method determines shear wave slowness of the formation. The method includes propagating quadrupole wave energy into the formation and detecting quadrupole dispersive waveforms received at a second location. Formation shear wave slowness is calculated using dispersive slowness time coherence processing
100 Citations
39 Claims
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1. A tool for generating signals indicative of shear wave slowness of the formation surrounding a borehole containing a fluid and a drill string, the tool adapted for use with a drill string having a plurality of drill collars jointed together, the tool comprising:
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a collar portion defining an axis and adapted for mounting in a drill string;
a quadrupole sonic transmitter mounted to the collar portion at a first location; and
a quadrupole sonic receiver array mounted to the collar portion at a second location, the second location spaced apart from the first location. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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- 8. A quadrupole sonic transmitter, for use in a tool for generating signals indicative of shear wave slowness of the formation surrounding a borehole containing a fluid and a drill string, the tool adapted for use in a drill string having a plurality of drill collars jointed together, said tool having a collar portion defining an axis, said quadrupole sonic transmitter having an azimuthal array of four equally spaced transducer quadrants, each quadrant including at least one electro-acoustical transducer element.
- 18. A quadrupole sonic receiver, for use in a tool for generating signals indicative of shear wave slowness of the formation surrounding a borehole containing a fluid and a drill string, the tool adapted for use in a drill string having a plurality of drill collars jointed together, said tool having a collar portion defining an axis, said quadrupole sonic receiver having an azimuthal array of four equally spaced transducer quadrants, each quadrant including at least one electro-acoustical transducer element.
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26. A system for determining shear wave slowness of the formation surrounding a borehole, the borehole containing a fluid, the system comprising:
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tool for generating signals indicative of formation shear wave slowness, the tool having a collar portion defining an axis and adapted for mounting in a drill string, a quadrupole sonic transmitter mounted to the collar portion at a first location, and a quadrupole sonic receiver array mounted to the collar portion at a second location, the second location spaced apart from the first location; and
computing means for calculating formation shear wave slowness from said signals. - View Dependent Claims (27)
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28. A method for determining shear wave slowness of the formation surrounding a borehole containing a drill string and a fluid, the method comprising:
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propagating quadrupole wave energy into the formation from a first location on the drill string;
detecting quadrupole dispersive waveforms at a second location on the drill string at a distance from the first location to obtain digital data indicative of shear wave slowness of the formation; and
calculating formation shear wave slowness from said digital data. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 39)
a) Fourier transforming at least a portion of said signals to obtain Fourier transformed signals;
b) backpropagating said Fourier transformed signals utilizing a plurality of quadrupole dispersion curves to obtain a plurality of sets of backpropagated signals;
c) stacking said backpropagated signals of each set to provide stacked sets; and
d) using said stacked sets to determine formation shear wave slowness.
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32. A method according to claim 31, further using formation quadrupole dispersive waveforms having a range of frequencies whose maximum frequency is approximately equal to the cut-off frequency for collar quadrupole mode propagation.
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33. A method according to claim 31, further using formation quadrupole dispersive waveforms having a range of frequencies whose minimum frequency is approximately equal to the frequency at which formation quadrupole mode is expected to propagate at a slowness approximately equal to the formation shear slowness.
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34. A method according to claim 31, wherein the pre-selected range of frequencies is approximately 4-8 kHz.
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35. A method according to claim 28, further comprising filtering for formation quadrupole mode data, wherein filtering includes frequency domain filtering.
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36. A method according to claim 28, further comprising filtering for formation quadrupole mode data, wherein filtering includes slowness domain filtering.
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37. A method according to claim 28, further comprising filtering for formation quadrupole mode data, wherein filtering includes frequency-slowness domain filtering.
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39. A method according to claim 36, further comprising filtering for formation quadrupole mode data.
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38. A method for determining shear wave slowness in formation surrounding a borehole containing a drill string and a fluid, the method comprising:
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a) obtaining from a plurality of sonic detectors, data indicative of formation shear wave slowness;
b) Fourier transforming at least a portion of said data to obtain Fourier transformed signals;
c) backpropagating said Fourier transformed data utilizing a plurality of quadrupole dispersion curves to obtain propagated data representing a plurality of sets of backpropagated signals;
d) stacking said backpropagated data to provide stacked sets data;
e) processing said stacked sets data to determine formation shear wave slowness.
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Specification