Downhole Fluid Composition Analysis Using NMR and Chromatography
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Solution Overview
Problem
Current methods for compositional analysis of hydrocarbon-containing fluids downhole, particularly those involving NMR and optical data, face limitations in accurately determining chain length distributions and fluid composition due to uncertainties in harsh subterranean environments and the presence of asphaltenes and dissolved gases, leading to overestimation of relaxation times and insufficient resolution for small chain lengths.
Innovation Solution
Combining NMR data with additional measurements from tools like gas chromatography and optical observation to enhance the resolution and accuracy of chain length distributions, using a piecewise log-linear scaling law with nodes at specific carbon chain lengths to model T2 relaxation times, and constraining inversion processes with data from multiple tools to improve the accuracy of fluid composition analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If NMR relaxation measurements are used to determine oil composition, then information about chain length distributions and viscosity can be obtained, but uncertainties are introduced due to the harsh subterranean environment and presence of asphaltenes
Solution Approach 1:
The patent combines NMR relaxation measurements with diffusion measurements and optical measurements to create a multi-parameter analysis system. This merging of different measurement techniques compensates for the limitations of individual methods, particularly the uncertainties introduced by asphaltenes and harsh downhole conditions, thereby improving the accuracy of chain length distribution determination
Solution Approach 2:
The patent introduces an intermediary computational model that uses measured NMR relaxation times and diffusion coefficients to calculate chain length distributions. This model acts as a mediator between the raw measurements and the final composition analysis, allowing the system to account for environmental factors and asphaltene effects through mathematical correction rather than direct measurement
2Productivity
If scaling laws are used to estimate chain length from T2 relaxation times, then composition analysis can be performed, but overestimation of relaxation times occurs leading to insufficient resolution for small chain lengths
Solution Approach 1:
The patent segments the chain length analysis into multiple ranges, applying different analytical approaches for different carbon number ranges. For small chain lengths (C1-C5), diffusion measurements and optical measurements are emphasized, while for larger chains, NMR relaxation measurements are more effective. This segmentation allows each measurement type to operate in its optimal range, improving overall precision
Solution Approach 2:
The patent adds the diffusion coefficient measurement dimension to complement the T2 relaxation time measurement. By measuring both relaxation and diffusion, the system obtains two independent parameters for each component, enabling more accurate chain length determination through joint inversion, particularly for small chain lengths where relaxation times alone are insufficient
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 provides a more robust and accurate determination of fluid composition, including chain length distributions and viscosity, by integrating data from multiple sources, effectively addressing the limitations of existing methods and improving the resolution and range of carbon chain length analysis.
Implementation Method 1
by using a nuclear magnetic resonance (NMR) tool to conduct a NMR relaxation measurement, a diffusion measurement, or both on the hydrocarbon-containing fluid
Implementation Method 2
using a non-NMR tool to conduct an additional measurement of a reference fluid to obtain non-NMR data wherein the additional measurement comprises gas chromatography
Implementation Method 3
wherein the additional measurement comprises gas chromatography, optical observation, or both
Data Source
AI summary
Apparatus and methods of analyzing a composition of a hydrocarbon-containing fluid including using a nuclear magnetic resonance (NMR) tool to conduct a NMR relaxation measurement, a diffusion measurement, or both on the hydrocarbon-containing fluid to obtain NMR data, using a non-NMR tool to conduct an additional measurement of a reference fluid to obtain non-NMR data wherein the additional measurement comprises gas chromatography, optical observation, or both, and using the NMR data and the non-NMR data in an inversion process to determine an indication of the composition of the hydrocarbon-containing fluid. In some embodiments, the indication is determined over 4 chain length nodes.