Dual-Crystal ATR Measurement of Refractive Index and Carbon Dioxide
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Solution Overview
Problem
Existing methods for determining the refractive index of formation fluids assume a fixed crystal material refractive index and non-dispersive fluid index, leading to errors due to wavelength-dependent variations, especially in high solute concentrations, which affect the accuracy of dissolved gas fraction inference.
Innovation Solution
A tool and method using two crystals with different refractive indices and angles of incidence for attenuated total reflection, continuously measuring light attenuation to determine the refractive index and carbon dioxide concentration in formation fluids, accounting for variations in refractive index with wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single crystal material with fixed refractive index is used for measurement, then the device complexity is reduced, but measurement precision deteriorates due to wavelength-dependent variations in refractive index
Solution Approach 1:
The measurement system is segmented into multiple crystal elements, each with different refractive indices. By dividing the measurement function across multiple crystals rather than relying on a single crystal, the system can account for wavelength-dependent variations in refractive index, thereby improving measurement precision while maintaining manageable device complexity
Solution Approach 2:
The invention changes the parameter of crystal refractive index by using multiple crystals with different refractive indices. This allows the system to measure and compensate for wavelength-dependent variations in the fluid's refractive index, improving measurement accuracy without requiring overly complex instrumentation
2Ease of operation
If the refractive index variation with wavelength is not accounted for, then the measurement process is simplified, but the accuracy of dissolved gas fraction inference deteriorates
Solution Approach 1:
The system uses feedback by measuring the refractive index at multiple wavelengths and using these measurements to correct for wavelength-dependent variations. This feedback mechanism allows the system to maintain measurement simplicity while improving the accuracy of dissolved gas fraction inference through iterative correction
Solution Approach 2:
The invention changes the measurement approach by incorporating wavelength-dependent refractive index measurements. This allows the system to account for variations in refractive index across different wavelengths, improving dissolved gas fraction accuracy without significantly complicating the measurement process
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
Improves the accuracy of refractive index and dissolved gas fraction measurements by correcting for wavelength-dependent variations, enabling real-time determination and reducing errors associated with fluid composition changes.
Implementation Method 1
The wavelength, the refractive indices, and the angles of incidence are configured such that the light undergoes total internal reflection at interfaces between the crystals and the formation fluid
Data Source
AI summary
Systems and methods presented herein generally relate to a tool for determining a refractive index of a formation fluid using attenuated total reflection. The tool includes a body having a fluid admitting assembly and a flow line that receives the formation fluid. The tool also includes two different crystals having faces in contact with fluid in the flow line. The tool further includes at least one light source coupled to the crystals and configured to direct light into the crystals. In addition, the wavelength, the refractive indices, and the angles of incidence are configured such that the light undergoes total internal reflection at interfaces between the crystals and the formation fluid. The tool also includes at least one light detector coupled to the crystals and configured to measure reflected light exiting the crystals. The tool further includes at least one processor coupled to the at least one light detector.