Steering Tool Positioning Using Magnetic Markers
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Solution Overview
Problem
Current steering tools for horizontal directional drilling face positional errors due to pitch and yaw measurement inaccuracies and underground magnetic field disturbances, leading to reduced accuracy in drilling path alignment, especially in challenging soil conditions and hard-to-reach locations like under rivers or lakes.
Innovation Solution
A system and method that incorporates a sensing arrangement within the steering tool to detect pitch and yaw orientations, combined with a processor using magnetic information from rotating dipole fields transmitted by markers along the intended drill path, to determine the tool's location with enhanced accuracy, allowing for customized position determination along the path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pitch and yaw measurements are used to determine drill head position through numerical integration, then the steering tool system can provide continuous position monitoring, but positional errors accumulate with increasing progress through the ground
Solution Approach 1:
The system employs a feedback mechanism where magnetic markers placed at known positions along the drill path provide periodic position verification. The drill head's magnetometer detects these markers, and the system uses the detected marker positions to correct accumulated integration errors, creating a closed-loop feedback system that maintains accuracy over long drilling distances.
Solution Approach 2:
Magnetic markers serve as intermediary reference objects placed along the drill path. These markers act as mediators between the drill head and the ground surface, providing known position references that enable error correction without requiring direct surface contact or complex external measurement systems.
2Measurement precision
If magnetic field sensing is used to determine drill head position, then position information can be obtained, but underground disturbances of the earth's magnetic field cause significant yaw measurement bias errors
Solution Approach 1:
The system changes the parameter being measured from absolute magnetic field orientation to relative position changes. Instead of relying on absolute yaw angles that are sensitive to magnetic disturbances, the system measures changes in magnetic field strength and direction as the drill head moves between known marker positions, making the measurement less sensitive to ambient magnetic field variations.
Solution Approach 2:
The system converts the presence of magnetic field disturbances into a benefit by using the changes in magnetic field characteristics between known marker positions as the measurement signal. The magnetic disturbances affect all measurements equally, but the differential measurement between two known positions eliminates the bias error.
3Ease of operation
If drill head orientation is used to determine travel direction, then steering control can be implemented, but in wet and sandy soil the orientation does not necessarily reflect the direction of travel
Solution Approach 1:
Magnetic markers serve as intermediary reference objects that provide direct position information independent of drill head orientation. These markers enable the system to determine actual travel direction by comparing expected position (based on orientation) with actual position (based on marker detection), providing a reference that is unaffected by soil conditions.
Solution Approach 2:
The system introduces asymmetry between the drill head orientation and actual travel direction by allowing them to diverge in difficult soil conditions. Rather than forcing them to match, the system independently measures both and uses the discrepancy to calculate actual position and provide corrective steering guidance.
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 system significantly reduces positional errors and enhances drilling accuracy by integrating magnetic information with pitch and yaw measurements, improving steering effectiveness even in difficult soil conditions and hard-to-reach locations.
Implementation Method 1
A receiver, forming another part of the steering tool, receives the rotating dipole field with the steering tool at a current one of the spaced apart positions to produce magnetic information
Data Source
AI summary
A steering tool is movable by a drill string to form an underground bore along an intended path. A sensing arrangement of the steering tool detects its pitch and yaw orientations at a series of spaced apart positions along the bore, each position is characterized by a measured extension of the drill string. The steering tool further includes a receiver. At least one marker is positioned proximate to the intended path, for transmitting a rotating dipole field to expose a portion of the intended path to the field for reception by the receiver. The detected pitch orientation, the detected yaw orientation and the measured extension of the drill string are used in conjunction with magnetic information from the receiver to locate the steering tool. The steering tool may automatically use the magnetic information when it is available. A customized overall position determination accuracy can be provided along the intended path.