Pulsed Eddy Current Sensor Array for Cased-Hole Inspection
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Solution Overview
Problem
Existing non-destructive inspection methods for tubing, such as electromagnetic devices, are inadequate for detecting wall thickness variations and multi-pipe azimuthal imaging in downhole logging applications, particularly due to limitations in signal penetration, signal-to-noise ratio, and the inability to effectively measure larger surrounding tubing.
Innovation Solution
A tube inspection system comprising a telemetry module, centralizing module, and inspection device with a sensor array including a center receiver coil, ferri-core, peripheral receiver, and transmitter coil, which induces an eddy current by producing an electromagnetic field and records voltage to analyze tubing characteristics, enhancing measurement accuracy and signal penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant eddy-current electromagnetic tools are used, then tubing integrity measurement is possible, but signal penetration through multiple tube walls is insufficient
Solution Approach 1:
The patent applies pulsed eddy-current excitation instead of constant excitation. The transmitter coil is activated in pulses, creating time-varying magnetic fields that induce eddy currents in the tube walls. This periodic action allows the system to penetrate multiple tube walls by using the decay characteristics of the eddy currents to distinguish between different wall depths, thereby improving signal penetration while maintaining measurement reliability.
2Difficulty of detecting and measuring
If transient electromagnetic methods using pulsed electromagnetic waves are used, then signal from second tube wall can be detected, but signal-to-noise ratio problems occur
Solution Approach 1:
The patent employs a differential sensor array with multiple receiver coils positioned at different locations and orientations. Each receiver coil is optimized for detecting eddy current signals from specific regions or wall depths. By using the differential characteristics of the sensor array, the system can locally enhance the signal-to-noise ratio for each detection zone, allowing accurate measurement of the second tube wall signal while suppressing noise through differential processing.
3Ease of operation
If electromagnetic devices are used for tube inspection, then operation insensitivity to fluid is achieved, but multi-pipe azimuthal imaging capability is lacking
Solution Approach 1:
The patent divides the inspection system into multiple independent receiver coils arranged in a differential array, with each coil capable of detecting eddy current signals from specific azimuthal positions and pipe walls. This segmentation allows the system to independently image multiple pipes and walls in the azimuthal direction while maintaining fluid insensitivity, as each receiver coil operates independently to detect local magnetic field variations.
4Measurement precision
If flux-leakage measurement methods are used, then localized damage detection in ferromagnetic pipes is possible, but measurement is hindered by thinning of tubing and strong flux coupling requirements
Solution Approach 1:
The patent replaces traditional flux-leakage measurement with pulsed eddy-current measurement. Instead of relying on magnetic flux coupling through the tube wall, the system uses time-varying magnetic fields to induce eddy currents directly in the conductive tube walls. This substitution eliminates the need for strong flux coupling and reduces sensitivity to thinning, as the eddy current method directly measures wall conductivity and thickness without requiring ferromagnetic materials or strong magnetic flux paths.
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 effectively measures tubing thickness, aberrations, and attached devices, providing higher accuracy in multi-pipe scenarios and overcoming previous limitations by boosting the electromagnetic field and optimizing signal reception.
Implementation Method 1
inducing an eddy current by producing an electromagnetic field
Implementation Method 2
inducing an eddy current within the tubing
Implementation Method 3
measuring voltage with a center receiver coil and a peripheral receiver
Data Source
AI summary
A system and method for inspecting a tube comprising a telemetry module, a centralizing module, an inspection device, a differential amplifier, a sensor array, and a service device. In embodiments, a tube inspection device may comprise a sensor array. The sensor array may further comprise a center receiver coil, a ferri-core, a peripheral receiver, and a transmitter coil. A method for inspection a tube may comprise inserting an inspection device into a tube, energizing a sensory array, inducing an eddy current within the tubing, and measuring voltage with a center receiver coil and a peripheral receiver of the sensor array.