Frozen DAS Chamber for Fiber Coupling and Signal Quality Tests
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Solution Overview
Problem
Conventional VSP deployment techniques using hydrophones, geophones, and accelerometers face limitations such as limited sensing aperture, high rig costs, and sensitivity to harsh environments, while DAS systems using optical fibers in wells suffer from reduced signal quality due to coupling issues with borehole fluids.
Innovation Solution
A frozen DAS system is used to test and optimize fiber configurations by manipulating fibers into desired shapes within a chamber filled with a freezable liquid, recording baseline measurements at room and frozen temperatures, and performing strain-sensing measurements to improve coupling and data quality, mimicking the properties of cementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sensors (hydrophones, geophones, accelerometers) are used in VSP deployment, then sensing capability is provided, but sensing aperture is limited and rig costs increase
Solution Approach 1:
The patent segments the sensing function by using multiple discrete sensors (hydrophones, geophones, accelerometers) distributed along the wellbore, where each sensor provides localized measurement capability while collectively covering the entire well length, thereby increasing sensing aperture without requiring a single complex sensor
2Reliability
If conventional sensors are used in VSP deployment, then sensing capability is provided, but rig time costs increase
Solution Approach 1:
The patent employs multi-functional sensors that can operate in various harsh wellbore environments (submerged, cased, uncased conditions) and perform multiple sensing functions (acoustic, vibrational, strain measurements), eliminating the need for specialized equipment for different deployment scenarios and reducing rig time
3Productivity
If optical fibers are deployed in wells for DAS, then distributed sensing along entire well length is achieved, but signal quality deteriorates due to coupling issues with borehole fluids
Solution Approach 1:
The patent changes the physical state of the coupling medium from liquid to solid by freezing the borehole fluid, which fundamentally alters the acoustic coupling properties between the optical fiber and the surrounding formation, thereby improving signal quality while maintaining distributed sensing coverage
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 method enhances fiber coupling to the subsurface, optimizing DAS data quality by simulating cementation conditions, reducing strain field interference, and improving measurement accuracy.
Implementation Method 1
freezing the freezable liquid
Implementation Method 2
freezing the freezable liquid
Data Source
AI summary
A method includes providing a distributed acoustic sensing (DAS) system and a fiber sample. The DAS system includes a chamber and a signal generator positioned proximate to and outside the chamber. The method further includes manipulating the fiber sample into a desired shape, filling the chamber with a freezable liquid, wherein the freezable liquid is provided at room temperature, and placing the fiber sample into the chamber. The method also includes recording a first set of room temperature baseline measurements, freezing the freezable liquid, and recording a first set of frozen baseline measurements. The method further includes performing strain-sensing measurements while the signal generator is active, and melting the freezable liquid.