Fiber Optic Cement Plug Locator Using Reel-Based Length Measurement
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Solution Overview
Problem
Current methods for determining the location of a cement plug in a wellbore are inaccurate, as they rely on volume displacement measurements, indication wires, mechanical flipper indicators, electromagnetic or magnetic signals, or complex fiber optic systems, which are prone to errors due to dimensional tolerances, aeration, compression, and strain issues.
Innovation Solution
An apparatus using a reel of wound optic fiber line attached to the plug, with a light transmitter/receiver device that measures signal changes at the second position, allowing for precise localization and displacement tracking without needing to measure along the entire fiber, and optionally incorporating sensors for environmental parameter monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If volume displacement measurements are used to determine plug location, then the measurement method is simple, but the measurement precision is poor due to dimensional tolerances, aeration, and compression
Solution Approach 1:
The patent replaces mechanical volume displacement measurement with an optical measurement system. A fiber optic cable is attached to the plug, and a laser transmitter/receiver measures the length of cable paid out as the plug descends. This optical system eliminates errors from dimensional tolerances, aeration, and compression that affect mechanical volume measurements, while maintaining operational simplicity.
2Device complexity
If indication wires or mechanical flipper indicators are used, then the device complexity is low, but the reliability is poor due to errors from aeration and compression
Solution Approach 1:
The patent replaces mechanical indication wires and flipper indicators with an optical fiber system. The fiber optic cable attached to the plug provides direct length measurement through laser time-of-flight or phase measurement, eliminating mechanical errors from aeration and compression while maintaining low device complexity through the use of a single attached cable.
3Ease of operation
If electromagnetic or magnetic signals are used for localization, then the ease of operation is improved, but the measurement precision deteriorates due to signal interference and compression
Solution Approach 1:
The patent replaces electromagnetic and magnetic signal systems with optical fiber-based measurement. The laser transmitter/receiver system measures the physical length of fiber cable paid out as the plug descends, providing immunity to signal interference and compression effects that plague electromagnetic systems, while maintaining ease of operation through surface-based monitoring.
4Measurement precision
If complex fiber optic systems are used, then the measurement precision is improved, but the device complexity increases due to strain issues and complex measurement along entire fiber
Solution Approach 1:
The patent extracts only the necessary portion of fiber optic technology. Instead of using complex distributed sensing along the entire fiber length, the system simply measures the total length of fiber cable paid out from the surface reel as the plug descends. This approach achieves high measurement precision while avoiding the complexity of strain compensation and distributed measurement systems.
Solution Approach 2:
The patent uses a simplified optical measurement approach that copies the essential function of complex fiber optic sensing systems. By measuring the length of fiber cable paid out rather than sensing along the entire fiber, the system achieves accurate location measurement without the complexity of full distributed fiber optic sensing systems.
5Ease of operation
If a reel of wound optic fiber line is used attached to the plug, then the ease of operation is improved and device complexity is reduced, but measurement precision may worsen if the entire fiber cannot be measured
Solution Approach 1:
The patent extracts only the essential measurement function from complex fiber optic systems. By measuring the total length of fiber cable paid out from the surface reel rather than attempting to measure along the entire fiber path, the system achieves both operational simplicity and measurement precision. The laser transmitter/receiver measures cable length directly without needing to account for fiber routing complexities.
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 and efficient localization of the plug within the wellbore, reducing errors and complexity, while allowing for real-time monitoring of environmental parameters like temperature and pressure, and facilitating precise cement displacement control.
Implementation Method 1
The location of the plug can be determined by sending a signal down the fiber to the plug and measuring the time it takes for the signal to get to the plug and bounce back
Data Source
AI summary
Fiber-optic cable systems are useful for locating a cementing apparatus in the wellbore, for example a cement plug. A reel of fiber-optic cable is attached to the cementing apparatus. At the surface the cable is attached to a stationary position where it is connected to a light transmitter/receive device. As the cementing apparatus travels down the cased wellbore, the cable unwinds, thereby changing the nature of the reflected light signal and allowing one to deduce the position of the cement plug within the well.