Magnetic Probe for Rod Defect Detection
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Solution Overview
Problem
Current methods for analyzing hollow drill rods and casings are complex and expensive, and fail to accurately detect non-rotationally symmetrical defects such as perforations or corrosion zones, due to limitations in magnetic field measurement and generation technologies.
Innovation Solution
A probe with a permanent magnet whose north-south axis is parallel to the rod axis, combined with magnetometers that detect axial, radial, and tangential components of magnetization, allowing for detailed analysis of defects regardless of orientation and symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a permanent magnet with north-south axis perpendicular to the rod axis is used (as in prior art), then the device complexity is reduced, but the measurement precision for non-rotationally symmetrical defects deteriorates
Solution Approach 1:
The patent applies asymmetry by orienting the permanent magnet's north-south axis parallel to the rod axis rather than perpendicular to it. This asymmetric orientation creates a magnetization pattern that breaks rotational symmetry, enabling the detection system to distinguish between rotationally symmetrical features (like joints) and non-rotationally symmetrical defects (like corrosion or perforations at specific radial zones). The asymmetric magnet configuration allows the magnetometers to detect variations in magnetic field distribution that reveal detailed defect characteristics.
2Measurement precision
If multiple magnetometer components (axial, radial, tangential) are added to detect all magnetization components, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent implements multi-functionality by using a single permanent magnet that simultaneously generates magnetization components in multiple directions (axial, radial, and tangential) within the rod. This unified magnetic field source enables all three magnetometer components to detect comprehensive magnetization information from one magnetic source, rather than requiring separate excitation mechanisms for each measurement direction. The permanent magnet serves multiple functions: creating axial magnetization for joint detection, radial magnetization for corrosion detection, and tangential magnetization for perforation detection.
3Power
If high current pulses are applied to create magnetic fields at great depth, then the power increases, but the loss of energy increases due to conductor resistance and heat dissipation limits
Solution Approach 1:
The patent applies self-service by utilizing the permanent magnet's intrinsic magnetic properties to generate the magnetic field without requiring external power supply or current pulses. The permanent magnet inherently maintains its magnetization and continuously generates the necessary magnetic field for defect detection as the probe moves through the rod. This eliminates the need for energy-intensive current pulse generation, conductor systems for deep power delivery, and associated heat dissipation management, particularly beneficial in high-temperature well environments.
4Power
If high current pulses are applied to excite coils at depth, then the power increases, but the device complexity increases due to required shielding for detonators
Solution Approach 1:
The patent extracts and eliminates the coil excitation system entirely by replacing it with a permanent magnet. This removes the source of high current pulses that would interfere with detonator operation, thereby eliminating the need for complex shielding arrangements around explosive charges. The permanent magnet provides the necessary magnetic field generation without electromagnetic interference, simplifying the overall device design and enabling safer operation in conjunction with explosives for rod unscrewing or casing perforation.
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
Enables the detection and analysis of both rotationally symmetrical and non-rotationally symmetrical defects, providing accurate measurements of defects like corrosion or perforations, and maintaining consistent results across multiple passes.
Implementation Method 1
a permanent magnet whose north-south axis is parallel to the axis of the rods and whose length is greater than the internal diameter of the rods
Implementation Method 2
The means for creating a magnetic field in a rod or a tube (which is generally made of a ferromagnetic material or other material capable of acquiring a remanent magnetization under the effect of a field)
Implementation Method 3
The means for measuring the magnetic field are generally means for measuring the magnetic flux which only operate if the probe is moving
Data Source
Figure 1~2
AI summary
The invention relates to a probe for analysing an assembly of rods including an elongate housing (1) supporting at a first end a permanent magnet (5), the north-south axis of which is parallel to the axis of the rods and, in a position sufficiently separated from said magnet, a set of magnetometers (7) for detecting axial, radial and tangential components of the magnetisation of the rods.