Mud turbine tachometer
First Claim
Patent Images
1. Apparatus for measuring the speed of a rotating element downhole in a well, including:
- magnetometer means for normally sensing at least a component of the earth'"'"'s magnetic field and generating a first signal commensurate therewith;
a rotating element, the speed of rotation of which is to be measured;
magnet means on said rotating element and positioned to superimpose a rotating magnetic field on the earth'"'"'s magnetic field, a frequency related parameter of said superimposed magnetic field being commensurate with the speed of rotation of said rotating element;
said magnetometer means sensing the rotating magnetic field superimposed on the earth'"'"'s magnetic field and generating a second signal which varies commensurate with said frequency related parameter; and
processing means for distinguishing said frequency related parameter of said second signal from said first signal to determine the speed of rotation of said rotating element.
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Abstract
In an MWD measurement system, the speed of rotation of a downhole turbine is measured by the interaction of a triaxial magnetometer in a sensor package and a permanent magnet attached to the turbine shaft. The triaxial magnetometer may be part of an existing MWD system for measuring borehole directional parameters. The magnet is a strong magnet mounted on the turbine shaft perpendicular to the axis of the turbine and the axis of the drill string.
60 Citations
32 Claims
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1. Apparatus for measuring the speed of a rotating element downhole in a well, including:
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magnetometer means for normally sensing at least a component of the earth'"'"'s magnetic field and generating a first signal commensurate therewith; a rotating element, the speed of rotation of which is to be measured; magnet means on said rotating element and positioned to superimpose a rotating magnetic field on the earth'"'"'s magnetic field, a frequency related parameter of said superimposed magnetic field being commensurate with the speed of rotation of said rotating element; said magnetometer means sensing the rotating magnetic field superimposed on the earth'"'"'s magnetic field and generating a second signal which varies commensurate with said frequency related parameter; and processing means for distinguishing said frequency related parameter of said second signal from said first signal to determine the speed of rotation of said rotating element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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12. Apparatus for measuring the speed of rotation of a turbine downhole in a well in a drill string, including:
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magnetometer means in the drill string for normally sensing at least a component of the earth'"'"'s magnetic field and generating a first signal commensurate with a directional parameter of the drill string; turbine means in said drill string having a central shaft defining the axis of rotation; magnet means on said turbine shaft and positioned to interact with said magnetometer means, said magnet means superimposing a rotating magnetic field on the earth'"'"'s magnetic field, the frequency of said rotating magnetic field being commensurate with the speed of rotation of said turbine said magnetometer means sensing the rotating magnetic field superimposed on the earth'"'"'s magnetic field and generating a second signal which varies in frequency commensurate with the speed of rotation of said turbine; and processing means for separating said first and second signals and determining the frequency of said second signal to determine the speed of rotation of said turbine. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification