Antenna-Based Well Casing Discontinuity Detection
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Solution Overview
Problem
Existing systems for behind-casing measurements in well systems face challenges in accurately detecting discontinuities, such as collar joints, during 'run-in-hole' operations without requiring permanent magnets or additional hardware, and struggle to maintain signal strength amidst noise.
Innovation Solution
A system that uses an antenna mounted on a tubing string with a voltage source and processing device to apply an AC voltage and monitor current changes, detecting discontinuities by comparing current levels when proximate to and away from the discontinuity, allowing for relative position indication without needing to move the tubing string.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensing devices are used to detect discontinuities, then discontinuity detection capability is improved, but the system requires the tubing string to move at high speed to maintain signal strength above noise level
Solution Approach 1:
The patent replaces the mechanical/magnetic sensing system with an electrical system. Instead of using magnetic sensors that require physical movement through the casing to generate detectable signals, the invention uses an antenna system that transmits electrical signals through the casing material itself. The discontinuity detection is achieved by monitoring changes in electrical current characteristics (amplitude, phase, impedance) rather than magnetic field changes, eliminating the need for high-speed mechanical movement.
Solution Approach 2:
The invention changes the detection parameter from magnetic field strength (which requires motion to vary) to electrical current characteristics (which vary with casing properties regardless of motion). By measuring changes in current amplitude, phase angle, or impedance of the antenna system as it interacts with different casing sections, the system can detect discontinuities at any speed including when stationary.
2Measurement precision
If permanent magnets and magnetic sensors are added to the tubing string, then discontinuity sensing capability is improved, but device complexity increases
Solution Approach 1:
The antenna system serves multiple functions: it provides discontinuity detection, enables communication between the tubing string and surface equipment, and can be used for other electromagnetic-based measurements. This multi-functionality eliminates the need for separate dedicated magnetic sensing hardware, reducing overall device complexity while maintaining discontinuity detection capability.
Solution Approach 2:
The casing itself serves as the transmission medium for the electromagnetic signals. The antenna system uses the casing material (which is already present in the wellbore) as part of the electrical circuit, eliminating the need for additional external reference structures or complex sensor assemblies. The system leverages existing components (casing, antenna) to achieve detection functionality.
3Reliability
If the tubing string is kept moving to maintain signal strength, then signal-to-noise ratio is improved, but the system cannot operate when stationary or at low speeds
Solution Approach 1:
The invention replaces motion-dependent magnetic sensing with an electrical field-based system that does not require relative motion between the sensor and the object being sensed. The antenna system generates electromagnetic fields that penetrate the casing and interact with discontinuities regardless of whether the tubing is moving or stationary, allowing operation across the full range of speeds including zero.
Solution Approach 2:
The system uses periodic electromagnetic signal transmission from the antenna to continuously probe the casing for discontinuities. By transmitting signals at regular intervals and analyzing the reflected or transmitted signal characteristics, the system maintains reliable detection capability whether the tubing is moving rapidly, moving slowly, or completely stationary, as each periodic signal provides a fresh measurement opportunity.
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 accurate detection of casing discontinuities and provides a relative position indication, allowing for precise tracking and counting of casing sections without additional hardware, and can operate at higher velocities or when stationary.
Implementation Method 1
electronic systems use antennas for power transfer and communication through the casing
Implementation Method 2
sense changes in magnetic fields
Data Source
AI summary
Detecting discontinuities in a well casing according to some aspects includes actively monitoring the electric current response in an antenna or in antennas during the insertion of a tubing string. The method does not require permanent magnets, or any hardware elements beyond those that are already present in a typical behind-casing measurement system. A system according to some aspects includes an antenna that is mounted in or on a tubing string and a voltage source that can be connected to the antenna. A processing device is connected to the antenna and the voltage source. The processing device applies an AC voltage to the antenna and monitors a current generated in the antenna while the AC voltage is being applied.