Gyroscopically-Oriented Survey Tool with Accelerometer Drift Correction
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Solution Overview
Problem
Current borehole survey tools face challenges in accurately determining azimuth due to sensitivity to shock loading, drift, and external magnetic fields in gyroscopic instruments, and measurement errors accumulate in integration-type instruments, while magnetically-oriented tools are unreliable at high geomagnetic latitudes.
Innovation Solution
A gyroscopically-oriented survey tool with a housing containing orthogonally-mounted accelerometers and pseudo-orthogonally-mounted gyroscopes, along with an optional magnetometer module, which uses accelerometer data to correct gyroscope data for drift and distortion, and corroborates azimuth measurements with magnetometer data when available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gyroscopes are used to measure azimuth, then measurement capability is provided, but sensitivity to shock loading and drift occurs
Solution Approach 1:
The patent combines gyroscopes with accelerometers in a single survey tool. The accelerometers measure gravitational vertical and tool orientation, providing reference data that can detect gyroscope drift and shock loading effects. This merged system allows cross-validation of measurements, where accelerometer-derived orientation serves as a check on gyroscope accuracy, thereby maintaining measurement precision while compensating for gyroscope reliability issues.
Solution Approach 2:
The system uses accelerometer measurements as feedback to monitor gyroscope performance. By continuously comparing gyroscope-derived orientation with accelerometer-derived orientation, the system can detect drift and shock loading effects in real-time. This feedback mechanism enables identification and correction of gyroscope errors, maintaining reliable azimuth measurement despite the inherent sensitivity of gyroscopes to environmental disturbances.
2Device complexity
If magnetometers are used to measure azimuth, then construction simplicity is achieved, but reliability at high geomagnetic latitudes deteriorates
Solution Approach 1:
The survey tool is designed with multi-functionality, incorporating both gyroscopes and accelerometers that can operate independently or together for azimuth determination. While magnetometers provide simple construction, the gyroscope-accelerometer combination serves as a universal solution that works reliably at all latitudes, including high geomagnetic latitudes where magnetic field methods fail. This multi-functional approach ensures the tool adapts to various operational conditions without sacrificing reliability.
3Device complexity
If integration-type instruments are used, then construction simplicity is maintained, but measurement accuracy deteriorates with hole depth
Solution Approach 1:
The patent replaces the mechanical integration method (physically running the instrument inside drill rods and mechanically accumulating curvature changes) with a sensor-based computational approach. Gyroscopes measure angular velocity, and through integration of these measurements, the system calculates orientation changes without physical contact with the borehole wall. This substitution maintains relatively simple instrument construction while dramatically improving measurement precision, as the gyroscope data does not accumulate errors with depth like mechanical integration methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The tool provides reliable borehole trajectory determination by correcting for sensor errors and drift, maintaining accuracy even under conditions of shock loading and magnetic interference, and effectively handles high geomagnetic latitudes.
Implementation Method 1
Sensing inclination is relatively straightforward. There is considerable prior art related to accelerometers and tiltmeters that can be used to determine the inclination of the instrument axis with the gravitational vertical.
Implementation Method 2
Current gyroscopically-oriented instruments are the most complex and expensive. Typically, they rely on one or two rotating-mass gyroscopes in a gimballed or strap-down mount. As the instrument is run through the borehole, movements of the axis (in the case of gimballed gyroscope) or precessive forces (in the case of a strap-down gyroscope) are measured to obtain the attitude of the instrument.
Implementation Method 3
Instruments using the Earth's magnetic field are of relatively simple construction and are therefore the least expensive. Unfortunately, magnetic fields generated by the drilling equipment and/or nearby mineralization can distort the local magnetic field, and hence the reported azimuth.
Data Source
AI summary
A gyroscopically-oriented survey tool, includes a housing having an axis. Three accelerometers are mounted in the housing with their axis set orthogonally. A first of the axis is aligned to the axis of the housing. A second of the axis is perpendicular to the first. A third of the axis is perpendicular to both of the first and the second. Three gyroscopes are mounted pseudo-orthogonally in the housing with their axis set at relative angles of other than 90 degrees. None of the axis of the gyroscopes are mounted parallel to the axis of the accelerometers. This configuration permits data from the accelerometers to be used to check the quality of data from the gyroscopes.