Radial Pick-Up Coil Arrangement for Well Casing Defectoscopy
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Solution Overview
Problem
Existing downhole electromagnetic defectoscopes struggle to accurately distinguish between defects on the inner and outer sides of tubing strings and fail to effectively track thickness variations, especially in extensive corrosion zones, due to mutual interference and limited sensitivity.
Innovation Solution
An apparatus with an electromagnetic field generation unit, radial pick-up coils with U-shaped cores, and a data acquisition and processing unit, featuring bipolar excitation and variable amplification, enhances sensitivity and accuracy by positioning pick-up coils radially symmetrically and using an integral pick-up coil wound on the same core as the exciter coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inductive pick-up coils are located circumferentially around the device, then defects can be detected in a wider radial sector, but mutual interference of the coils increases
Solution Approach 1:
The device segments the detection function by using one axial pick-up coil and two transverse pick-up coils with different orientations, allowing each coil to detect specific defect types without mutual interference while collectively providing comprehensive detection coverage
Solution Approach 2:
Each pick-up coil is assigned a specific functional role: the axial coil detects longitudinal defects, while the two transverse coils detect transverse defects with different orientations. This local specialization eliminates mutual interference while maintaining comprehensive detection capability
2Adaptability or versatility
If inductive pick-up coils are arranged perpendicularly to the exciter coil magnetic axis, then defects in a wider radial sector can be detected, but the coils are sensitive only to deviations of uniform magnetic field, reducing sensitivity to thickness variations
Solution Approach 1:
The invention uses asymmetric coil orientations - one axial coil and two transverse coils at different angles - rather than symmetric perpendicular arrangements. This asymmetry allows the coils to detect both magnetic field deviations and direct thickness variations, improving measurement precision while maintaining wide detection coverage
3Power
If a single-pole magnetising pulse current is used in the exciter coil, then eddy currents are generated in the pipe, but the pick-up coils cannot track thickness variations on long spans of the surveyed pipe
Solution Approach 1:
The invention adds a new dimension to the detection capability by incorporating pick-up coils with different orientations (axial and transverse). This multi-dimensional arrangement allows the system to detect both magnetic field deviations and direct thickness variations, enabling tracking of thickness variations on long spans that single-orientation coils cannot detect
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 solution improves defectoscopy accuracy by enabling precise detection of defects and thickness variations, allowing for better estimation of pipe thickness and decentring, while reducing noise and mutual interference, thus enhancing the informative value of measurements.
Implementation Method 1
an electromagnetic field generation unit for generation of an excitation pulse of a specified amplitude and duration
Implementation Method 2
pick-up sensor unit with an integral pick-up coil and a plurality of radial pick-up coils
Implementation Method 3
An alternating current is fed into the exciter coil to generate loop eddy currents in the surrounding steel pipe, and those, in turn, induce an EMF in pick-up coils
Data Source
AI summary
The apparatus is useful for monitoring integrity of casings, tubings, and other tubular strings in oil and gas wells. An apparatus for defectoscopy of downhole casings includes several units in a housing. An electromagnetic field generation unit generates excitation pulse of a specified amplitude and duration. It includes an exciter coil containing a core made a high magnetic permeability material. A pick-up sensor unit includes an integral pick-up coil and radial pick-up coils mounted around the exciter coil winding. Each pick-up coil has a U-shaped core with poles directed perpendicularly to the surveyed pipe surface and having a center line parallel to the center line of the exciter coil winding. A data control, acquisition, and processing unit includes operational amplifiers with variable amplification factors and analog-to-digital converters (ADCs) that transmit signals from the pick-up coils to software for casing defect analysis.