Downhole Fluid Spectral Extraction for GOR Accuracy
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Solution Overview
Problem
The presence of water in formation fluid samples significantly affects the estimated gas-oil ratio (GOR) during drilling operations, particularly for Logging While Drilling (LWD) measurements, necessitating improved methods for analyzing these fluids.
Innovation Solution
A downhole fluid sampling and evaluation measurement tool that flows formation fluid through a flowline and makes optical absorption measurements to generate optical density spectra. By applying predetermined selection criteria based on optical density values at specific wavelengths, the tool selects representative spectra of pure hydrocarbon or water phases, allowing for accurate estimation of fluid properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical absorption measurements are made on formation fluid samples containing water, then fluid composition analysis can be performed, but the water significantly degrades the accuracy of gas-oil ratio (GOR) estimates
Solution Approach 1:
The patent segments the fluid sample analysis by separating water-related spectral features from hydrocarbon-related spectral features. By identifying and isolating water absorption bands at specific wavelengths (1450 nm, 1940 nm, 2100 nm) from the overall spectrum, the method enables independent analysis of water content and hydrocarbon composition, thereby eliminating water's harmful effect on GOR estimation accuracy
Solution Approach 2:
The patent extracts and removes the water spectrum component from the mixed fluid spectrum. By taking out the water absorption characteristics at identified wavelengths and subtracting them from the total absorption spectrum, the method isolates the pure hydrocarbon signal, enabling accurate GOR estimation even when water is present in the formation fluid sample
2Measurement precision
If dewatering algorithms are applied to mitigate water effects, then GOR estimation accuracy improves, but the complexity of the analysis process increases
Solution Approach 1:
The patent applies local quality by focusing analysis only on specific wavelength regions where water and hydrocarbons have distinct absorption characteristics. Rather than applying complex algorithms across the entire spectrum, the method identifies key wavelength bands (1450 nm, 1940 nm, 2100 nm for water; other regions for hydrocarbons) and performs targeted spectral decomposition, simplifying the overall computational process while maintaining high accuracy
Solution Approach 2:
The patent changes the analysis parameter from attempting to model the entire complex mixed spectrum to focusing on specific absorption coefficient ratios at selected wavelengths. By measuring absorption at discrete wavelength points and calculating simple ratios or differences, the method transforms a complex spectral analysis problem into a series of straightforward quantitative comparisons, reducing algorithmic complexity
3Object-affected harmful factors
If multiple spectral wavelengths are analyzed to identify pure phase spectra, then water interference is reduced, but the measurement time and data processing requirements increase
Solution Approach 1:
The patent performs preliminary action by pre-identifying and storing the characteristic water absorption wavelengths (1450 nm, 1940 nm, 2100 nm) and their corresponding spectral signatures before actual fluid analysis. This preliminary characterization of water's spectral fingerprint allows the system to quickly recognize and subtract water interference during real-time measurements, reducing the time required for spectral analysis without sacrificing 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
This method effectively mitigates the impact of water on GOR estimates by identifying pure phase spectra, leading to more accurate composition analysis and improved field planning decisions.
Implementation Method 1
making optical absorption measurements on the flowing formation fluid to generate a plurality of optical density spectra
Data Source
AI summary
A method for evaluating a formation fluid includes flowing formation fluid through a flowline in a downhole fluid sampling and evaluation measurement tool deployed in a wellbore and making optical absorption measurements on the flowing formation fluid to generate a plurality of optical density spectra. A spectrum from the plurality of generated spectra is selected using predetermined selection criteria that are based on optical density values at one or more selected wavelengths in the generated spectra. At least one fluid property is estimated from the selected spectrum.