Gimbal Sensor Platform for High-Inclination Wellbore Surveying
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Solution Overview
Problem
Existing downhole survey tools face challenges in accurately determining the orientation and position of a wellbore at high inclinations due to limitations in single-axis gyroscopes and sensor errors, such as bias and mass unbalance, which affect the determination of true north and toolface angles.
Innovation Solution
A gimbal sensor platform with an outer and inner gimbal, coupled with angular positioning devices and a gyro, allows for multiple measurements at various orientations to improve accuracy by rotating the gimbal axes and utilizing a combination of sensors like accelerometers and magnetometers to correct for errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-axis gyro is used to detect Earth's rotation at high inclination, then the device complexity is reduced, but the measurement precision of true north determination deteriorates
Solution Approach 1:
The system divides the measurement task into multiple segments by using multiple single-axis gyros instead of one complex multi-axis gyro. Each gyro measures Earth's rotation along a specific axis, and the results are combined through mathematical processing to determine true north, achieving high precision while maintaining simple individual sensor design
Solution Approach 2:
The system transitions from measuring in a single dimension (one gyro axis) to measuring in multiple dimensions by deploying multiple gyros with different axis orientations. This dimensional expansion allows the system to overcome the limitations of single-axis measurement at high inclinations and accurately determine true north through multi-dimensional data fusion
2Device complexity
If gyro readings are taken without error detection mechanisms, then the device complexity is reduced, but the reliability of orientation determination deteriorates due to undetected bias errors and mass unbalance
Solution Approach 1:
The system implements feedback mechanisms where gyro readings are continuously monitored and compared against expected values. When discrepancies indicating bias errors or mass unbalance are detected, the system generates corrective feedback to adjust measurements or trigger recalibration, ensuring reliable orientation determination while maintaining relatively simple hardware through intelligent error detection algorithms
3Device complexity
If cross-axial accelerometers are used to measure gravity signal at low inclination, then the measurement precision deteriorates due to small gravity signal, but the device complexity remains simple
Solution Approach 1:
The system dynamically adapts its measurement strategy based on inclination angle. At low inclinations where cross-axial accelerometer signals are weak, the system switches to using gyro-based measurements which remain effective. This dynamic switching between measurement modes maintains high precision across all inclination angles while keeping the sensor configuration relatively simple
4Measurement precision
If gyro or magnetic toolface is used at low inclination, then the measurement precision of toolface angle is improved, but the reliability deteriorates due to inability to detect sensor errors
Solution Approach 1:
The system merges multiple measurement approaches (accelerometer-based gravity toolface, gyro-based toolface, and magnetic toolface) into a unified measurement system. By combining these methods, the system achieves high precision at low inclinations through gyro and magnetic measurements while simultaneously gaining error detection capability through the redundancy and cross-validation provided by multiple measurement modalities
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
Enhances the accuracy of wellbore orientation and position determination, especially at high inclinations, by compensating for sensor errors and providing precise measurements of the Earth's spin vector and magnetic field.
Implementation Method 1
The gyrocompass utilizes one or more gyroscopic sensors, referred to herein as gyros to detect the Earth's rotation and determine the direction to true north from the downhole tool
Implementation Method 2
Accelerometers may be used to detect the local gravity field, typically dominated by the Earth's gravity, to determine the direction to the center of the Earth
Implementation Method 3
Magnetometers may similarly be used to detect the local magnetic field, typically dominated by the Earth's magnetic field, to determine the direction to magnetic north
Data Source
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AI summary
A gimbal sensor platform positionable in a tool body includes an inner gimbal and an outer gimbal. The inner gimbal is rotatably coupled to the outer gimbal, and the outer gimbal is rotatably coupled to the tool body. The inner and outer gimbals may each be rotated by an angular positioning device. A gyro or other sensor may be coupled to the inner gimbal. The gyro or other sensor may be reoriented by rotating the outer gimbal, the inner gimbal, or both.