Near-bit tool attitude measurement while drilling apparatus and method
First Claim
1. A near-bit tool attitude measurement while drilling method, comprising:
- (1) installing a measurement-while-drilling (MWD) apparatus in a bottomhole assembly near a bottom of a drill string above a near-bit stablizer,wherein the MWD apparatus comprises a plurality of measurement sensors coupled to a measurement circuit, wherein the plurality of measurement sensors include a triaxial accelerometer, a triaxial gyroscope, a triaxial magnetic sensor, and a temperature sensor,wherein the measurement circuit comprises a plurality of low-pass filters coupled to an analog-to-digital converter, a field programmable gate array coupled to the analog-to-digital convertor, a processor coupled to the field programmable gate array, a memory coupled to the processor, andwherein each of the triaxial accelerometer, the triaxial gyroscope, the triaxial magnetic sensor, and the temperature sensor is coupled to one of the plurality of low-pass filters;
(2) measuring data of the triaxial accelerometer, the triaxial gyroscope, the triaxial magnetic sensor, and the temperature sensor using the MWD apparatus;
correcting measured data of the triaxial accelerometer and the triaxial magnetic sensor by utilizing measured data of the temperature sensor, respectively; and
calculating a first attitude angle by utilizing corrected measured data of the triaxial accelerometer and the triaxial magnetic sensor;
(3) initializing quaternions by utilizing the first attitude angle;
(4) correcting measured data of the triaxial gyroscope by utilizing the measured data of the temperature sensor;
performing time updating on initialized quaternions according to the measured data of the triaxial gyroscope; and
further calculating a second attitude angle by utilizing the updated quaternions;
(5) measuring data of the triaxial gyroscope, and repeating the step (4) to calculate a third attitude angle; and
(6) after 1 s to 10 s, going to the step (2), calculating the first attitude angle by reusing the data of the triaxial accelerometer and the triaxial magnetic sensor, initializing the quaternions by using the first attitude angle, and periodically initializing the quaternions to eliminate cumulative errors of the triaxial MEMS gyroscope.
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Abstract
A near-bit tool attitude MWD apparatus includes measurement sensors and a measurement circuit. The measurement sensors transmit measured signals to the measurement circuit, and the measurement circuit processes and calculates the signals to obtain attitude data. The measurement sensors include a triaxial accelerometer, a triaxial gyroscope, a triaxial magnetic sensor and a temperature sensor, the measured data of the triaxial accelerometer, the triaxial gyroscope and the triaxial magnetic sensor are respectively corrected using the measured data of the temperature sensor, a first attitude angle is calculated using the corrected measured data of the triaxial accelerometer and the triaxial magnetic sensor. Quaternions are initialized using the first attitude angle, and the initialized quaternions are subjected to time updating according to the measured data of the triaxial gyroscope, and further an attitude angle is calculated utilizing the updated quaternions. The quaternions are periodically initialized to eliminate cumulative errors of the triaxial gyroscope, so as to improve the near-bit tool attitude MWD accuracy.
19 Citations
10 Claims
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1. A near-bit tool attitude measurement while drilling method, comprising:
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(1) installing a measurement-while-drilling (MWD) apparatus in a bottomhole assembly near a bottom of a drill string above a near-bit stablizer, wherein the MWD apparatus comprises a plurality of measurement sensors coupled to a measurement circuit, wherein the plurality of measurement sensors include a triaxial accelerometer, a triaxial gyroscope, a triaxial magnetic sensor, and a temperature sensor, wherein the measurement circuit comprises a plurality of low-pass filters coupled to an analog-to-digital converter, a field programmable gate array coupled to the analog-to-digital convertor, a processor coupled to the field programmable gate array, a memory coupled to the processor, and wherein each of the triaxial accelerometer, the triaxial gyroscope, the triaxial magnetic sensor, and the temperature sensor is coupled to one of the plurality of low-pass filters; (2) measuring data of the triaxial accelerometer, the triaxial gyroscope, the triaxial magnetic sensor, and the temperature sensor using the MWD apparatus;
correcting measured data of the triaxial accelerometer and the triaxial magnetic sensor by utilizing measured data of the temperature sensor, respectively; and
calculating a first attitude angle by utilizing corrected measured data of the triaxial accelerometer and the triaxial magnetic sensor;(3) initializing quaternions by utilizing the first attitude angle; (4) correcting measured data of the triaxial gyroscope by utilizing the measured data of the temperature sensor;
performing time updating on initialized quaternions according to the measured data of the triaxial gyroscope; and
further calculating a second attitude angle by utilizing the updated quaternions;(5) measuring data of the triaxial gyroscope, and repeating the step (4) to calculate a third attitude angle; and (6) after 1 s to 10 s, going to the step (2), calculating the first attitude angle by reusing the data of the triaxial accelerometer and the triaxial magnetic sensor, initializing the quaternions by using the first attitude angle, and periodically initializing the quaternions to eliminate cumulative errors of the triaxial MEMS gyroscope. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification