Optical Seismic Sensor Flexure Mass Design
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Solution Overview
Problem
Conventional seismic sensors fail in harsh environmental conditions of deep boreholes, such as high temperatures and corrosive fluids, making it challenging to accurately measure microseismic events, which are crucial for monitoring reservoir conditions during enhanced oil recovery operations.
Innovation Solution
An optical seismic sensor system with a sensor device that includes a reference mass constrained to move relative to a frame via a flexure, changing the length of an optical conduit, allowing for unidirectional movement and minimizing crosstalk, and is optically connected to a surface unit for signal processing, eliminating electronic components prone to failure in harsh environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electronic sensors are used in deep boreholes, then they can detect and communicate earth motion, but they fail in harsh environmental conditions such as high temperatures and corrosive fluids
Solution Approach 1:
The patent replaces electronic sensing components with an optical interferometer system. The sensor device includes a reference mass constrained by flexures and an optical module that measures seismic disturbances through optical interference patterns, eliminating electronic components that fail in harsh environments. The optical system uses light interference to detect displacement, providing reliability in high-temperature and corrosive conditions where electronic sensors fail.
Solution Approach 2:
The patent changes the operating parameter regime by using optical frequencies instead of electrical signals for sensing and communication. The optical interferometer operates with light waves, allowing the system to function in temperature ranges and chemical environments that would destroy electronic components, thus adapting the sensor to harsh borehole conditions.
2Measurement precision
If optical interferometry is used to detect small displacements, then measurement precision is improved, but device complexity increases due to the need for precise optical alignment and reference mass constraints
Solution Approach 1:
The patent segments the optical system into distinct functional modules: a reference mass component, flexure constraint mechanisms, an optical module with interferometer, and optical conduit connections. This modular segmentation allows each component to be optimized independently and simplifies assembly and alignment, reducing overall system complexity while maintaining measurement precision.
Solution Approach 2:
Instead of constraining the optical components and allowing the mass to move freely, the patent inverts the approach by constraining the reference mass through flexures and allowing the optical system to adapt to the mass position. This inversion simplifies the optical alignment requirements while maintaining precise displacement measurement capability.
3Measurement precision
If a reference mass is allowed to move freely to detect seismic disturbances, then measurement sensitivity is improved, but crosstalk between different directions of seismic disturbance increases
Solution Approach 1:
The patent introduces asymmetry through the flexure constraint geometry, which is designed to allow motion primarily in one direction while providing strong constraint in perpendicular directions. This asymmetric flexure design enables the reference mass to respond sensitively to seismic disturbances along the desired measurement axis while minimizing crosstalk from orthogonal directions, achieving directional selectivity.
Solution Approach 2:
The patent applies local quality by designing the flexure constraints with different mechanical properties in different directions. The flexures are engineered to be compliant along the measurement axis (allowing sensitive detection) while being stiff in perpendicular directions (blocking crosstalk). This directional differentiation of mechanical properties achieves both sensitivity and isolation from unwanted directions.
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 system enables reliable and cost-effective seismicity monitoring by decoupling seismic disturbances from different directions, providing accurate measurements of seismic data without electronic components that fail in harsh conditions, and can operate in temperatures up to 300°C.
Implementation Method 1
Optical interferometry is a common technique used to measure small displacements of an object relative to a reference
Implementation Method 2
a reference mass attached to the frame via at least one flexure, such that movement of the reference mass relative to the frame is constrained to a single predetermined path
Data Source
AI summary
Disclosed is an optical seismic sensor system for measuring seismic events in a geological formation, including a surface unit for generating and processing an optical signal, and a sensor device optically connected to the surface unit for receiving the optical signal over an optical conduit. The sensor device includes at least one sensor head for sensing a seismic disturbance from at least one direction during a deployment of the sensor device within a borehole of the geological formation. The sensor head includes a frame and a reference mass attached to the frame via at least one flexure, such that movement of the reference mass relative to the frame is constrained to a single predetermined path.