EMAT Acoustic Signal Measurement Using Modulated Gaussian Wavelet and Hilbert Demodulation
AssigneeBaker Hughes Incorporated
InventorJinsong Zhao
Life of this patent
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Abstract
Casing signals generated by an EMAT in a borehole are processed using at least two orthogonal band-limited filters. The band-limited filters may include Gaussian or Cauchy Wavelet filters. By using the Hilbert transform, an envelope of the filtered signals is determined and amplitudes and arrival times of individual arrivals are estimated. These can be used to estimate casing and cement properties.
Claims23
A method of characterizing a casing installed in a borehole in an earth formation, the method comprising:
- activating a transducer at least one azimuthal orientation in the borehole and generating an acoustic pulse;
- receiving a signal comprising a plurality of events resulting from the generation of the acoustic pulse;
- bandpassing the received signal using two modulated filters, the two modulated being orthogonal to one another, and providing a bandpassed signal;
- estimating an envelope of the bandpassed signal;
- and
- estimating from the envelope of the bandpassed signal an arrival time of each of the plurality of events, the arrival times being characteristic of a property of at least one of:
- (i) the casing, and (ii) a cement in an annulus between the casing and the formation.
An apparatus for characterizing a casing installed in a borehole in an earth formation, the apparatus comprising:
- a transducer configured to generate an acoustic pulse at least one azimuthal orientation in the borehole;
- a receiver configured to receive a signal comprising a plurality of events resulting from the generation of the acoustic pulse;
- and
- at least one processor configured to:
- bandpass the received signal using two modulated filters, the two modulated filters being orthogonal to one another, and provide a bandpassed signal;
- estimate an envelope of the bandpassed signal;
- and
- estimate from the envelope of the received signal an arrival time of each of the plurality of events, the arrival times being characteristic of a property of at least one of:
- (i) the casing, and (ii) a cement in an annulus between the casing and the formation.
A non-transitory computer-readable medium product accessible to at least one processor, the non-transitory computer-readable medium product including instructions which enable the at least one processor to characterize a property of a casing in a borehole in an earth formation using a signal comprising a plurality of events resulting from generation of an acoustic pulse by a transducer in the borehole, the instructions including bandpassing the signal using two modulated Gaussian functions, the two modulated Gaussian functions being orthogonal to one another, estimating an envelope of the bandpassed signal and estimating from the envelope an arrival time of each of the plurality of events.
Dependencies are inferred from the claim text.