Distributed Acoustic Sensor for Downhole Plug Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In downhole wellbore operations, determining the accurate location of top plugs during cementing is challenging due to leaks, compressible fluids, and inefficient pumping, leading to inaccurate pressure measurements and potential contamination of cement.
Innovation Solution
A system utilizing distributed acoustic sensors with fiber optic cables and coherent optical time-domain reflectometers to detect acoustic noise caused by plug movement, enabling real-time tracking of plug location and rate of motion within the wellbore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pressure increase measurement is used to determine top plug location, then the measurement method is simple, but the measurement precision deteriorates due to leaks and compressible fluids
Solution Approach 1:
The patent replaces the mechanical pressure measurement system with an acoustic detection system using distributed acoustic sensors (DAS). Instead of relying on pressure increases that are affected by leaks and compressible fluids, the system uses acoustic signals generated by the plug interacting with the wellbore environment to determine plug location, thereby achieving more precise measurements independent of fluid leaks.
Solution Approach 2:
The patent introduces acoustic signals as an intermediary medium to detect plug location. The acoustic signals serve as a mediator between the plug and the detection system, allowing indirect but accurate measurement of plug position without being affected by the direct mechanical pressure issues that plague traditional methods.
2Productivity
If displacement fluid is pumped to move the top plug, then the plug can be displaced through the wellbore, but fluid leaks around the plug cause loss of substance and reduce measurement accuracy
Solution Approach 1:
The patent implements a feedback mechanism where acoustic sensors continuously monitor the plug's position and provide real-time information about plug movement and potential leaks. This feedback allows operators to detect fluid leakage around the plug and adjust displacement fluid pumping rates accordingly, optimizing plug displacement efficiency while minimizing fluid loss.
Solution Approach 2:
The patent replaces reliance on displacement fluid mechanics with acoustic field-based detection. Instead of depending on fluid pressure to track plug position (which is compromised by leaks), the system uses acoustic signals that can detect plug location even when fluid leaks are present, thereby decoupling measurement accuracy from fluid integrity.
3Device complexity
If traditional pressure monitoring is used to track plug movement, then the system complexity is low, but the reliability deteriorates due to inaccurate location determination
Solution Approach 1:
The patent replaces the simple but unreliable mechanical pressure monitoring system with an acoustic-based detection system. Although this increases device complexity, it dramatically improves reliability by providing accurate plug location determination that is not affected by fluid leaks, compressible fluids, or incorrect volume calculations.
Solution Approach 2:
The patent introduces acoustic signals as an intermediary to reliably detect plug position. These acoustic intermediaries provide trustworthy information about plug location and movement, overcoming the limitations of direct pressure monitoring and enabling reliable cementing operation control.
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
Provides accurate, real-time monitoring of plug location and movement, reducing uncertainty and improving the efficiency and accuracy of cementing operations by detecting acoustic signatures from strain in the fiber optic cables.
Implementation Method 1
A coherent optical time-domain reflectometer may detect acoustic signatures from strain in the fiber optic cable
Implementation Method 2
phase differences in an optical signal sent down the fiber optic cable may be caused by an acoustic event close to the fiber optic cable
Data Source
AI summary
A downhole well system can use a fiber optic cable that can be positioned downhole along a length of a wellbore. The well system may include a top plug, a bottom plug, or both that are used to contain a cement slurry during a cementing operation. The movement of the top plug and bottom plug may cause acoustic noise along the downhole portion of the casing. A reflectometer may detect the acoustic noise from strain in the fiber optic cable and determine a location of the top plug or bottom plug downhole.