Measuring micro stalls and stick slips in mud motors using fiber optic sensors
First Claim
1. A method of measuring stick slips and micro stalls in a down-hole mud motor, the method comprising:
- positioning in a borehole a mud motor with an elastomeric stator and at least one fiber optic sensor within the elastomeric stator, the fiber optic sensor including a Bragg grating;
measuring a spectrum of light reflected from the Bragg grating with a spectrophotometer;
processing, via a down-hole computer, data from the spectrophotometer to compute time-domain samples of peak wavelength in the spectrum of light reflected from the Bragg grating;
receiving a measurement from the fiber optic sensor corresponding to a strain within the elastomeric stator; and
processing, via the down-hole computer, the received measurement to determine frequencies of micro stalls and stick slips of the mud motor by converting the time-domain samples of peak wavelength to the frequency domain.
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Accused Products
Abstract
A fiber optic sensor is disposed in the elastomer of the stator of the mud motor in order to sense elastomer strain while drilling. The frequencies of micro stalls and stick slips are measured from the fiber optic sensor data by classification using thresholds or by converting time-domain measurements from the fiber optic sensor data to frequencies. For example, the frequencies are produced by accumulating a histogram over an interval of time or by computing a Discrete Fourier Transform over an interval of time. A plurality of fiber optic sensors also can sense angular position of the rotor of the mud motor for correlation of the micro stalls and stick slips with the angular position. The measurements of the micro stalls and stick slips are used to select remedial action such as changes in drilling parameters.
29 Citations
18 Claims
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1. A method of measuring stick slips and micro stalls in a down-hole mud motor, the method comprising:
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positioning in a borehole a mud motor with an elastomeric stator and at least one fiber optic sensor within the elastomeric stator, the fiber optic sensor including a Bragg grating; measuring a spectrum of light reflected from the Bragg grating with a spectrophotometer; processing, via a down-hole computer, data from the spectrophotometer to compute time-domain samples of peak wavelength in the spectrum of light reflected from the Bragg grating; receiving a measurement from the fiber optic sensor corresponding to a strain within the elastomeric stator; and processing, via the down-hole computer, the received measurement to determine frequencies of micro stalls and stick slips of the mud motor by converting the time-domain samples of peak wavelength to the frequency domain. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for measuring stick slips and micro stalls of a down-hole mud motor, the system comprising:
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a downhole mud motor having a rotor, an elastomer stator, and a fiber optic sensor disposed in the elastomer of the stator, the fiber optic sensor including a Bragg grating; a spectrophotometer coupled to the fiber optic sensor; and a computer communicably coupled to the fiber optic sensor, wherein the computer has a data processor and a computer-readable storage device storing instructions that, when executed by the data processor, cause the data processor to process data from the spectrophotometer to compute time-domain samples of peak wavelength in a spectrum of light reflected from the Bragg grating, and process a measurement from the fiber optic sensor corresponding to a strain within the elastomer stator to determine frequencies of the micro stalls and stick slips of the mud motor by converting the time-domain samples of peak wavelength to the frequency domain. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A non-transitory computer-readable storage device storing instructions that, when executed by a data processor, cause the data processor to
receive data from a fiber optic sensor disposed in a mud motor having a rotor and an elastomer stator, wherein the fiber optic sensor is disposed in the elastomer stator of the mud motor and the fiber optic sensor includes a Bragg grating; -
process the received data corresponding to a strain within the elastomer stator to determine frequencies of the micro stalls and stick slips of the mud motor by processing data from a spectrophotometer to compute time-domain samples of peak wavelength in a spectrum of light reflected from the Bragg grating, and by converting the time-domain samples of peak wavelength to the frequency domain; and report the determined frequencies of the micro stalls and stick slips. - View Dependent Claims (18)
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Specification