Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Well logging
Reexamination Certificate
1998-06-26
2001-03-27
McElheny, Jr., Donald E. (Department: 2862)
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Well logging
C702S014000, C367S014000
Reexamination Certificate
active
06208585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sonic or acoustic tools including a calibration and/or testing device for tuning or calibrating acoustic receivers and associated electronics or testing the stability and integrity of acoustic receivers and associated electronics.
More particularly, the present invention relates to acoustic downhole tools including a transmitter, an isolator, a receiver, associated electronics and a calibration device for dynamic receiver calibration and receiver/electronic integrity and/or stability testing. The present invention also relates to methods of making and methods of using the tool.
2. Description of the Related Art
In general, the apparatus for making an acoustic log consists of a transmitter capable of providing acoustic impulses, and at least one receiver responsive to acoustic energy, both mounted on a support for movement through the length of a well bore. The transmitter and receiver are spaced apart by a fixed distance and as the support is moved through the well bore, the energy from the acoustic pulses periodically generated by the transmitter is picked up by the receiver after transmission through and reflection from the well bore. The amplitudes of the received signals are correlated with the depth in the well bore to provide a log indicating the qualities of the cement bonding to the bore over the length of the well.
The acoustic transmitter and receiver(s) employed for these purposes typically comprise a piezoelectric or magnetostrictive element which converts periodic electric impulses into acoustic waves corresponding to the frequency of the periodic electric impulses and having an amplitude generally proportional to the energy of the electric impulses. The receiver, on the other hand, receives acoustic waves impinging thereon converting the pressure waves into an electric signal generally proportional to the intensity of the acoustic wave energy or amplitude. Thus, the receiver and transmitters work essentially in the opposite format.
For effective operation of these components, it is necessary that they both be efficiently coupled to the surrounding media and at the same time carefully protected or insulated from deleterious effects of liquids and gases present in well bores or casing. As the tool move through the well bore, the tools will encounter numerous changes in heat and pressure and spurious acoustic and vibrational disturbances which can result in tool malfunctions or calibration drifts.
One major drawback to present acoustic or sonic tools is the lack of ability to calibrate or even test the receivers and associated electronics for integrity or stability during down hole operations. Numerous U.S. Patents disclose acoustic or sonic LWD tools including, for example, U.S. Pat. Nos. 3,213,415, 4,809,236, 5,197,038 and 5,485,431, but none address real time calibration and integrity testing of the receiver portion of the tool.
Therefore, there is a need in the art for improved sonic tools having receiver testing and calibration capabilities. Moreover, there is a need in the art for improved sonic tools allowing dynamic testing and/or tuning of the receivers incorporated in the tools. Furthermore, there is a need in the art for methods of testing receiver responses or to tune or calibrate the receivers during routine operation.
SUMMARY OF THE INVENTION
The present invention provides a sonic tool including a transmitter, an isolator, a receiver, associated electronics and a novel calibration device operatively associated (in acoustic communication) with the receiver(s) designed to dynamically test the stability and integrity of the receiver(s) or to dynamically calibrate or tune the receiver(s).
The present invention also provides a receiver unit including a receiver and a novel calibration device operatively associated (in acoustic communication) with the receiver where the calibration device is designed to dynamically test the stability and integrity of the receiver or to dynamically calibrate or tune the receiver. The receiver unit can include a plurality of receivers each in acoustic communication with a calibration device.
The present invention further provides a calibration device generally including an acoustic transmission medium in acoustic communication with a receiver and an acoustic signal generator operatively coupled to the medium. When an acoustic signal is generated by the generator, it propagates through the medium to the receiver resulting in a receiver response which can be used to dynamically calibrate or tune the receiver, or dynamically test receiver stability and/or integrity.
The present invention provides a method for dynamically calibrating or testing a receiver unit of a sonic tool. The method includes generating an acoustic signal in an acoustic transmission medium in acoustic communication with the receiver and monitoring a response of the receiver to the generated acoustic signal. The method can further include calibrating the receiver unit based on its response to the acoustic calibration signal.
The present invention also provides a method for making a sonic tool including an internal calibration unit associated therewith. The method includes contacting a receiver unit of a sonic tool with an acoustic signal transmission medium in contact with an acoustic calibration signal generator capable of generating an acoustic signal.
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patent: 5233568 (1993-08-01), Kan et al.
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patent: 5842149 (1998-11-01), Harrell et al.
patent: 5936913 (1999-10-01), Gill et al.
Gilbreth J. M.
Gilbreth Mary A.
Gilbreth & Associates P.C.
Halliburton Energy Service,s Inc.
McElheny Jr. Donald E.
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