Leaky Coaxial Cable Fluid Interface Detection in Wells
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Solution Overview
Problem
Existing methods for detecting fluid levels in wells require in-well instrumentation, which is prone to failures, electronic drift, and high operational costs, and do not effectively measure fluid interfaces without deploying downhole gauges or optical fibers.
Innovation Solution
A detection device using a rigid coaxial cable with apertures or slots as antennas, transmitting and receiving electromagnetic signals to determine fluid interfaces without in-well instrumentation, utilizing Frequency Domain Reflectometry and Frequency-Modulated Continuous Wave techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-well instrumentation (downhole gauges, wireline, optical fibre) is deployed to detect fluid levels, then measurement capability is improved, but device complexity and operational costs increase
Solution Approach 1:
The patent replaces mechanical in-well instrumentation with an electromagnetic detection system. A coaxial cable is suspended in the wellbore to serve as a waveguide, and electromagnetic signals are transmitted through the cable to detect fluid levels based on dielectric property changes. This substitution eliminates the need for complex downhole gauges, wireline systems, or optical fibre deployments, thereby reducing installation complexity while maintaining measurement capability.
2Measurement precision
If in-well instrumentation is deployed to measure fluid interfaces, then measurement capability is improved, but reliability decreases due to electronic drift and failures
Solution Approach 1:
The patent replaces electronic in-well instrumentation with an electromagnetic wave-based detection system. The coaxial cable functions as a passive waveguide that transmits electromagnetic signals without active electronics downhole. Fluid levels are detected by measuring changes in dielectric properties along the cable, which affect signal propagation. This eliminates electronic drift and failure modes associated with downhole gauges and sensors, significantly improving operational reliability.
3Measurement precision
If in-well instrumentation is deployed to detect fluid levels, then measurement capability is improved, but operational costs increase
Solution Approach 1:
The patent replaces expensive in-well instrumentation with a cost-effective electromagnetic detection system using a standard coaxial cable as a waveguide. The system requires no complex downhole electronics, power supplies, or specialized sensors. The cable can be deployed simply by suspension in the wellbore, and fluid levels are detected through electromagnetic signal analysis. This dramatically reduces both initial installation costs and ongoing operational expenses while maintaining measurement capability.
4Device complexity
If electromagnetic signals are transmitted through a coaxial cable waveguide to detect fluid levels, then device complexity is reduced, but measurement precision may be affected by mode changes
Solution Approach 1:
The patent applies local quality by creating a controlled measurement environment within the coaxial cable waveguide. The cable structure confines electromagnetic energy to specific propagation modes, and fluid level detection is performed by analyzing local changes in dielectric properties at specific positions along the cable. This localized approach ensures that mode changes are controlled and predictable, allowing accurate measurement despite the simplified system architecture.
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 and measurement of fluid levels and interfaces within wells, reducing installation complexity and operational risks while providing robust and cost-effective monitoring.
Implementation Method 1
an electromagnetic pulse is radiated from a transmitter to an interface between two fluids and a reflection of the electromagnetic pulse from the interface is detected at a receiver
Implementation Method 2
The interface reflection is generally a resultant of the differential of dielectric properties of the structure being measured
Implementation Method 3
as an electromagnetic pulse is transmitted through a waveguide, it is known that the mode or modes, TEnn, will change until a dominant mode for the structure being scanned is formed
Data Source
AI summary
A material level detection device for detecting a material level includes a cable or transmission line having a coaxial cable and an electromagnetic transmitter and receiver arrangement connected or connectable to the cable or transmission line. The cable or transmission line acts as an antenna and includes an inner conductor and an outer conductor having a plurality of apertures or slots provided in a spaced relation along at least part of a length of the outer conductor. The inner conductor is provided within the outer conductor. The cable or transmission line is configured as a radiating cable and/or a leaky feeder, or leaky cable or hybrid of a leaky cable with a standard/nonleaky cable. The transmitter and receiver arrangement is connected or connectable to the inner conductor.