Rotary Steerable Tool Steering via Accelerometer Orientation
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Solution Overview
Problem
Rotary steerable tools face challenges in accurately determining the orientation of their housing and actuators due to interference from strong magnetic fields generated by the tool itself, which affects the accuracy of magnetic compass readings used for steering in directional drilling operations.
Innovation Solution
The implementation of a magnetic tool face direction determination system that uses a compass unit with a direction sensor to calculate the magnetic tool face, combined with fixed rotational offsets and periodic measurements of the shaft and housing offsets, allows for accurate computation and steering of the tool string, even in the presence of strong magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic compass is used to determine tool orientation in a rotary steerable system, then the system can maintain drill string rotation and avoid sticking, but the strong magnetic field generated by the tool itself interferes with the accuracy of magnetic compass readings
Solution Approach 1:
The patent uses accelerometers as intermediary sensors to measure tool orientation. Instead of relying solely on magnetic compass readings that are corrupted by the tool's own magnetic field, the system employs accelerometers to detect gravitational and inertial forces, providing an alternative measurement path that is not affected by magnetic interference. This intermediary measurement method allows the system to maintain reliable orientation data despite the harmful magnetic field.
Solution Approach 2:
The patent changes the measurement parameter from magnetic field detection to acceleration detection. By using accelerometers that measure gravitational and inertial forces rather than magnetic fields, the system avoids the interference problem entirely. This parameter change allows orientation measurement to proceed accurately even in the presence of strong magnetic fields generated by the rotary steerable tool.
2Ease of operation
If the drill string is halted for direction change (slide drilling), then the bent housing can be oriented to deflect the bit, but the non-rotating drill string is subject to sticking in the wellbore
Solution Approach 1:
The patent implements a dynamic steering system where the entire drill string rotates continuously while directional control is achieved through a steerable component that can change orientation dynamically. The system uses actuators to adjust the orientation of the steering element in real-time during rotation, allowing direction changes without halting drill string rotation. This dynamic approach eliminates the sticking problem associated with static slide drilling while maintaining precise direction control.
Solution Approach 2:
The patent pre-orients the steerable component (such as a bent sub or deflection device) to the desired direction before drilling begins. The orientation of this component is predetermined and set during assembly or prior to operation, allowing the drill string to rotate continuously while the pre-oriented component guides the bit in the correct direction. This preliminary orientation eliminates the need to halt rotation for direction changes.
3Measurement precision
If accelerometers are used to aid the compass in determining horizontal magnetic field component, then accuracy improves in hole angles above 5° inclination, but the system complexity increases
Solution Approach 1:
The patent uses accelerometers for multiple functions: they not only aid in determining the horizontal component of the magnetic field but also directly measure tool orientation relative to gravity, provide data for calculating inclination and azimuth, and can detect dynamic movements. This multi-functionality justifies the added complexity by providing comprehensive measurement capabilities from a single sensor type that is not affected by magnetic interference.
Solution Approach 2:
The patent replaces or supplements magnetic field-based orientation determination with acceleration-based measurement. By using accelerometers to measure gravitational and inertial forces, the system substitutes a mechanical measurement approach (sensing acceleration forces) for the electromagnetic approach (sensing magnetic fields). This substitution provides robust orientation data that is independent of magnetic field conditions, reducing overall system complexity in magnetic environments.
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
This solution enables precise orientation determination and steering of the rotary steerable tool, maintaining accuracy within +/−1 degree, thereby overcoming the limitations of traditional magnetic compass reliance and ensuring effective directional control during drilling.
Implementation Method 1
the compass unit measures the direction of its reference location relative to a reference direction (e.g., magnetic north)
Implementation Method 2
the shaft position sensor periodically determines the rotational position of the shaft relative to the housing
Data Source
AI summary
A method and system for steering a rotary steerable tool in a borehole. A method includes determining an azimuthal angle between a reference direction and a reference point on a direction determination component of a tool string. The direction control component is remote from the rotary steerable tool. The azimuthal angle and a time at which the angle was determined are communicated to a rotary steerable tool direction control system. A steerable shaft of the rotary steerable tool is deflected based on the azimuthal angle and the time at which the angle was determined, thereby directing the rotary steerable tool in a predetermined direction.