Evanescent Wave Gas Detection in Downhole Fluids
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Solution Overview
Problem
Current downhole measurement technologies face limitations in precision and accuracy for fluid analysis in boreholes, particularly in detecting gas concentrations and impending kicks, due to the complexity of fluid interactions and the need for precise waveguide positioning and signal-to-noise ratio optimization.
Innovation Solution
The use of evanescent wave measurement instruments with waveguides formed within a bulk substrate, utilizing Bragg gratings and femtosecond laser pulsing to create precise waveguide geometries that interact with downhole fluids, allowing for precise measurement of fluid properties and gas concentrations by generating evanescent waves and optimizing signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If waveguides are positioned close to the borehole wall for better fluid interaction, then measurement precision improves, but the risk of damage from downhole conditions worsens
Solution Approach 1:
The waveguide is segmented into a sensing region (exposed to fluid for measurements) and a protected region (shielded within the borehole). This segmentation allows the waveguide to simultaneously achieve close fluid interaction for precision measurements while protecting vulnerable portions from damaging downhole conditions.
Solution Approach 2:
The borehole wall acts as an intermediary barrier between the waveguide and the harsh downhole environment. By positioning the waveguide against the borehole wall, the wall provides natural protection while still allowing evanescent wave interaction with formation fluids, thus protecting the waveguide from direct exposure to damaging conditions.
2Device complexity
If waveguide dimensions are reduced to minimize interaction region, then device complexity reduces, but measurement precision worsens
Solution Approach 1:
The waveguide is designed with varying dimensions along its length: a first portion with larger dimensions optimized for evanescent wave generation and fluid interaction, and a second portion with smaller dimensions for protection and reduced complexity. This local variation in geometry allows each section to serve its specific function optimally.
Solution Approach 2:
The invention transitions from considering only waveguide cross-sectional dimensions to incorporating the longitudinal dimension as well. By varying the waveguide dimensions along its length (first portion vs. second portion), the design optimizes both measurement precision in the interaction region and device simplicity in the protected region.
3Measurement precision
If multiple waveguides are used to improve measurement accuracy, then measurement precision improves, but device complexity worsens
Solution Approach 1:
Multiple waveguides in the array serve multiple functions simultaneously: they provide redundant measurements for improved precision, enable detection of different gas concentrations through varying interaction lengths, and allow for calibration references. This multi-functionality justifies the increased complexity by delivering enhanced measurement capabilities.
Solution Approach 2:
The waveguides in the array are designed with different interaction lengths (different dimensions along the borehole wall), creating a range of sensitivity parameters. This parameter variation allows the system to detect gas concentrations across different ranges and provides built-in calibration capabilities, improving overall measurement precision despite the added complexity.
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
This approach enhances the accuracy and precision of downhole fluid analysis, enabling effective detection of gas concentrations and impending kicks, thereby improving well control and drilling efficiency by providing real-time, reliable measurement data.
Implementation Method 1
an evanescent wave arising from electromagnetic energy propagating in a segment of the waveguide
Implementation Method 2
The interaction may result in absorption of at least a portion of the electromagnetic energy propagating in the waveguide
Implementation Method 3
Waveguide may include Bragg grating, which may be written on the interior of the waveguide. Waveguide may include Bragg grating configured to produce a reflection spectrum matching a spectral property detected by the detector
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Methods, systems, devices, and products for estimating a parameter of interest of a downhole fluid in a borehole intersecting an earth formation. Apparatus include evanescent wave measurement instruments, which may include a substrate configured for contact with a downhole fluid such that at least a portion of the substrate is immersed in the downhole fluid; a waveguide formed in an interior of the substrate and having a configuration geometrically configured to generate an interaction between the downhole fluid and an evanescent wave arising from electromagnetic energy propagating in a segment of the waveguide; and a detector configured to generate measurement information indicative of the downhole fluid in response to electromagnetic signals received from the waveguide responsive to the interaction. The interaction may result in absorption of at least a portion of the electromagnetic energy propagating in the waveguide. The waveguide may be written in the substrate using laser pulses.