Magnetic Flux Leakage Casing Inspection Liftoff Correction
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Solution Overview
Problem
Magnetic flux leakage tools used for oil and gas well casing inspection face challenges in accurately detecting defects due to the sensor liftoff effect, which distorts magnetic field measurements and affects image quality, with existing methods failing to effectively correct for this issue.
Innovation Solution
The method involves measuring magnetic flux leakage data, determining sensor liftoff data, and performing outward analytic continuation and extrapolation to correct for sensor liftoff, using techniques such as linear or polynomial extrapolation to determine the magnetic field distribution at zero liftoff and integrate the normal component to shape defect visualization, and applying deconvolution inversion filters to improve image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic flux leakage tools are used for casing inspection, then defect detection capability is improved, but sensor liftoff effect distorts measurements and reduces accuracy
Solution Approach 1:
The patent applies parameter changes by using analytic continuation to transform the magnetic field data from the sensor plane to the casing surface plane. This mathematical transformation changes the spatial parameters of the data, effectively removing the liftoff effect and restoring measurement accuracy without requiring physical contact between sensor and casing.
Solution Approach 2:
The patent introduces an intermediary mathematical process (analytic continuation and extrapolation) that acts as a mediator between the distorted sensor measurements and the true casing defect characteristics. This intermediary transformation removes the liftoff distortion while preserving the defect signal.
2Area of stationary object
If multiple pads with azimuthally distributed sensors are used to cover the entire casing wall, then coverage is improved, but data processing complexity increases
Solution Approach 1:
The patent merges the data from multiple pads and multiple field components (radial, axial, azimuthal) into a unified processing framework. By applying analytic continuation to the combined dataset, the method simplifies the processing of multi-pad, multi-component data while maintaining comprehensive casing wall coverage.
Solution Approach 2:
The patent creates a universal processing approach that handles all field components (radial, axial, azimuthal) and all pad locations through a single analytic continuation framework. This multi-functional method eliminates the need for separate processing of different data types, reducing overall complexity.
3Measurement precision
If magnetic field sensors are placed in proximity to the pipe surface to detect defects, then detection sensitivity is improved, but the liftoff gap distorts the magnetic field measurements
Solution Approach 1:
The patent converts the harmful liftoff effect into a beneficial mathematical transformation problem. By recognizing that the liftoff effect creates a specific mathematical relationship between the sensor plane and the casing surface, the patent uses analytic continuation to transform the distorted measurements into accurate defect images, effectively turning the distortion into a solvable mathematical challenge.
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 approach enhances the accuracy of defect detection by removing the sensor liftoff effect, sharpening images, and providing a more precise interpretation of casing defects, allowing for improved inspection and analysis of corroded areas.
Implementation Method 1
Magnetic flux leakage tools are widely used for high-resolution casing corrosion inspection in oil and gas wells. Flux leakage generally relates to a distortion of the magnetic flux that has been introduced into a casing by an electromagnet or permanent magnet.
Implementation Method 2
an axially polarized permanent magnet or electromagnet is placed at the center of a casing tube to excite a magnetostatic field traversing through and saturating the steel casing
Implementation Method 3
The magnetic field sensor is typically a Hall effect sensor, a GMR (giant magneto-resistive) sensor or may be any other device measuring the magnetic field strength
Implementation Method 4
The magnetic field sensor is typically a Hall effect sensor, a GMR (giant magneto-resistive) sensor or may be any other device measuring the magnetic field strength
Data Source
AI summary
Embodiments of the present disclosure are directed towards a method for obtaining and analyzing flux leakage data. Embodiments may include measuring, using a magnetic flux leakage tool, magnetic flux leakage data from a casing and determining sensor liftoff data from the flux leakage data. Embodiments may also include performing outward analytic continuation of the magnetic flux leakage data from a sensor plane to one or more additional planes and extrapolating back from the one or more additional planes to a surface. Embodiments may include applying a model-based parametric inversion to the magnetic field flux leakage data and determining, based upon, at least in part, the model-based parametric inversion, a shape and size of a corresponding corroded area associated with the casing.