NIR Water Cut Sensing for Calibration-Free Saline Oil-Water Flow
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Solution Overview
Problem
Existing water cut (WC) sensors in the oil industry face challenges in achieving accurate measurements across a wide dynamic range (0-100%) without requiring calibration, especially in saline oil-water mixtures, and existing methods are either invasive, require frequent calibration, or pose safety concerns.
Innovation Solution
A laser-based NIR spectroscopy system that uses a composite absorbance spectrum analysis to determine water cut by computing a slope between oil-water and reference fluid spectra, eliminating interference from non-water species, enabling calibration-free WC sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microwave resonance is used to detect water cut, then water cut measurement can be performed, but sensitivity to water cut is poor
Solution Approach 1:
The patent replaces microwave resonance technology with near-infrared spectroscopy technology. The NIR sensor measures water cut by detecting the absorbance of near-infrared light by water molecules in the oil-water mixture, eliminating the poor sensitivity issues of microwave resonance while maintaining non-intrusive inline measurement capability.
Solution Approach 2:
The patent changes the measurement parameter from microwave frequency resonance to near-infrared light absorbance. By operating in the near-infrared spectral region where water has strong absorption features, the system achieves high sensitivity to water cut variations without requiring calibration, directly addressing the sensitivity and reliability problems of previous methods.
2Measurement precision
If microwave transmission is used to measure water cut, then water cut can be detected, but the measurement is obfuscated in saline oil-water mixtures
Solution Approach 1:
The patent substitutes microwave transmission with near-infrared spectroscopy. The NIR technology measures water cut based on the absorbance characteristics of water molecules, which are not affected by salinity-induced signal attenuation. This replacement eliminates the harmful effect of saline mixtures on measurement accuracy.
Solution Approach 2:
The patent uses near-infrared light as an intermediary measurement medium that penetrates the oil-water mixture without being attenuated by salinity. The light interacts with water molecules through absorbance, providing a clear measurement signal even in highly saline conditions where microwave transmission fails.
3Ease of operation
If planar microwave resonance is implemented on pipeline surface, then in situ non-intrusive water cut sensing is achieved, but calibration is required to identify oils present
Solution Approach 1:
The patent replaces planar microwave resonance with near-infrared spectroscopy technology. The NIR sensor measures water cut directly through the pipeline wall based on light absorbance, eliminating the need for calibration. The method uses the inherent absorbance characteristics of water in the near-infrared region, which are consistent and do not depend on oil type identification.
Solution Approach 2:
The patent enables the system to self-calibrate by using the inherent absorbance properties of water molecules in the near-infrared region. The measurement automatically adapts to different oil types and water cuts without requiring external calibration standards or manual adjustment, making the system self-sufficient across diverse operating conditions.
4Measurement precision
If near-infrared spectroscopy is employed with Beer-Lambert law adaptation, then more accurate water cut sensing is achieved, but frequent well-specific calibration is required which becomes tedious with well-aging and changing geolocation
Solution Approach 1:
The patent implements a calibration-free measurement system that uses the consistent absorbance characteristics of water molecules in the near-infrared region. The system automatically adapts to different wells and geolocations without requiring frequent recalibration, eliminating the time loss associated with manual calibration while maintaining high measurement accuracy throughout the well's operational life.
Solution Approach 2:
The patent changes the measurement approach from calibrated absorbance ratios to direct water-cut-based absorbance calculations. By using the known molar absorptivity of water in the near-infrared region and measuring total absorbance, the system directly calculates water cut without requiring well-specific calibration curves, thereby eliminating calibration time requirements while maintaining accuracy.
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 WC measurements across the full dynamic range with minimal interference from oil species, temperature, and salinity effects, without the need for calibration, ensuring robust and continuous monitoring.
Implementation Method 1
A laser-based spectroscopy system that obtains a composite absorbance spectrum of the oil-water flow and a reference absorbance spectrum, computes a slope to determine water cut
Implementation Method 2
Near-infrared (NIR) spectroscopy has been employed based on adapting Beer-Lambert law for non-homogeneous immiscible mixtures
Data Source
AI summary
A method for water cut sensing in an oil-water flow involves obtaining a composite absorbance spectrum of the oil-water flow, obtaining a reference absorbance spectrum of a reference fluid, computing a slope for data points associated with the composite absorbance spectrum of the oil-water flow vs corresponding data points associated with the reference absorbance spectrum of the known fluid, and based on the slope, determining the water cut of the oil-water flow.