Oscillating Path Length Spectrometer for Fluid Analysis
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Solution Overview
Problem
Spectroscopic compositional analysis of flowing fluids with time-varying compositions is challenging due to non-absorbance related optical effects such as scattering, which complicates the measurement of fluid properties like oil, water, and gas fractions in hydrocarbon wells, as existing methods struggle to distinguish true absorbance from scattering-induced baseline shifts.
Innovation Solution
The method involves oscillating the path length of a light beam through the fluid at a specific frequency, using a lock-in amplifier and band-pass filtering to separate true absorbance from scattering effects, allowing for accurate estimation of fluid parameters by measuring the ratio of light intensities at minimum and maximum path lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectroscopic methods are used to analyze flowing fluids, then the measurement process is simple, but scattering effects cause baseline shifts that reduce measurement precision
Solution Approach 1:
The patent applies periodic action by oscillating the light path length at a known frequency rather than using a static path length. This modulation creates a periodic signal that can be distinguished from scattering effects through frequency-selective detection, allowing the true absorbance signal to be extracted despite the presence of scattering-induced baseline shifts in the flowing fluid.
Solution Approach 2:
The patent implements feedback through the use of a lock-in amplifier that references the oscillation frequency. The system continuously monitors the modulated signal and uses the known oscillation frequency as a reference to extract the true absorbance signal, effectively compensating for scattering effects and maintaining measurement precision in flowing fluid conditions.
2Measurement precision
If the path length is oscillated to separate absorbance from scattering effects, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent uses periodic action by oscillating the light path length at a known frequency. This modulation technique allows the system to distinguish true absorbance signals from scattering effects through frequency-selective detection, improving measurement precision while adding only moderate complexity through the oscillation mechanism and synchronous detection circuitry.
Solution Approach 2:
The patent replaces complex mechanical separation methods with an optical field-based approach. Instead of physically separating scattering and absorbance components, the system uses frequency modulation and lock-in detection to extract the absorbance signal from the total signal, reducing mechanical complexity while maintaining or improving measurement precision.
3Loss of information
If conventional static path length measurement is used, then the system is simple to operate, but it cannot distinguish true absorbance from scattering effects in flowing fluids
Solution Approach 1:
The patent applies periodic action by oscillating the light path length at a known frequency. This creates a modulated signal where the true absorbance information is encoded at the oscillation frequency, allowing it to be extracted through frequency-selective detection. This resolves the information loss problem by enabling distinction between true absorbance and scattering effects in flowing fluids.
Solution Approach 2:
The patent implements feedback through lock-in detection that references the oscillation frequency. The system continuously compares the modulated signal against the known oscillation pattern, extracting the true absorbance information while rejecting scattering effects. This feedback mechanism prevents information loss by ensuring accurate recovery of the absorbance signal even in complex flowing fluid conditions.
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 enables real-time estimation of fluid parameters like oil, water, and gas fractions with improved accuracy, reducing the impact of scattering and allowing for precise modeling of downhole fluid compositions and formations.
Implementation Method 1
The time-dependent intensity may be indicative of a decrease in intensity between the light beam and the incident light
Implementation Method 2
non-absorbance related optical effects such as scattering, which complicates the measurement of fluid properties
Data Source
AI summary
Evaluating a fluid, including transmitting a light beam through the fluid to a detector while oscillating a path length traveled through the fluid by the light beam at a first frequency of oscillation; measuring a time-dependent intensity of incident light at the detector responsive to an interaction of the light beam with the fluid to produce a time-dependent intensity signal; filtering the time-dependent intensity signal to recover a path-dependent signal oscillating at the first frequency and indicative of an absorbance property of the fluid; and estimating a parameter of interest of the fluid using the path-dependent signal. The time-dependent intensity may be indicative of the true absorbance at multiple wavelengths of the fluid or fluids over the maximum path length difference so as to permit quantification of the percentages of each of these fluids. Filtering may include frequency filtering alone or using a phase-sensitive lock-in amplifier.