NMR Molecular Size Estimation via Mean Chain Length Scaling
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Solution Overview
Problem
Conventional NMR well logging techniques cannot accurately estimate the mean size of molecules in oil mixtures due to the lack of a straightforward correlation between molecule size and diffusion coefficients and relaxation times, which are also pressure and temperature dependent.
Innovation Solution
Developing a method to estimate and display molecular size information using NMR maps and logs by creating a scale based on the relationship between molecular size and diffusion or relaxation coefficients, allowing for the calculation of mean chain length and other molecular properties, such as hydrodynamic radius and hydrocarbon number, using 2D and 1D NMR maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional NMR well logging techniques are used to measure diffusion coefficients and relaxation times, then these measurements can be obtained, but they cannot accurately estimate the mean size of molecules in oil mixtures due to lack of straightforward correlation
Solution Approach 1:
The patent introduces mean chain length as an intermediary parameter that mediates between diffusion coefficients/relaxation times and molecular size. By establishing the relationship D ∝ N^(-α) and T2 ∝ N^(-β) where N is mean chain length, the patent creates a bridge that enables molecular size estimation from NMR measurements through this intermediate property.
Solution Approach 2:
The patent transforms the measurement approach by changing from direct molecular size measurement to measuring mean chain length through diffusion coefficients and relaxation times. It introduces power-law relationships with adjustable exponents (D ∝ N^(-α), T2 ∝ N^(-β)) that can be calibrated for different oil types, enabling accurate molecular size estimation through parameter transformation.
2Measurement precision
If diffusion coefficients and relaxation times are used to determine molecule size, then measurements can be obtained, but the results depend on pressure and temperature making it difficult to deduce molecule sizes
Solution Approach 1:
The patent performs preliminary calibration by establishing the relationships between diffusion coefficients, relaxation times, and mean chain length at known pressure and temperature conditions. By pre-determining the exponents α and β in the power-law relationships through calibration, the system accounts for pressure and temperature effects in advance, enabling accurate molecular size estimation under varying reservoir conditions.
3Measurement precision
If 2D NMR maps are used to measure diffusion and relaxation times, then these measurements can be obtained, but no straightforward correlation exists to estimate mean chain length without knowledge of the remaining mixture
Solution Approach 1:
The patent creates a universal method that works for different oil types and mixture compositions by establishing general power-law relationships (D ∝ N^(-α), T2 ∝ N^(-β)). The exponents α and β can be calibrated for different oil types, making the method universally applicable to various mixture compositions without requiring detailed knowledge of the remaining mixture components.
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
Enables accurate estimation of molecular size and properties like mean chain length, independent of temperature and pressure, providing a measure of basic substance properties and aiding in identifying oil types and composition gradients.
Implementation Method 1
nuclear magnetic resonance (NMR)
Implementation Method 2
diffusion coefficients of the fluid inside the area
Implementation Method 3
longitudinal (T1) and transverse (T2) relaxation times
Data Source
AI summary
Estimating and displaying information about the size of molecules within a substance from nuclear magnetic resonance (NMR) maps and/or logs. Methods include utilizing a relationship between the molecular size (e.g., mean chain length), and either a moment of diffusion or a relaxation distribution, to create a scale on a two-dimensional map. In one case, applying the relationship between the molecular size, and either a moment of diffusion or a relaxation distribution, to one-dimensional diffusion or relaxation distributions for the purpose of estimating the mean chain length of molecules within the substance. In another case, a method includes determining mean chain lengths of molecules within a substance and providing a one-dimensional NMR log showing the mean chain lengths at a plurality of depths. In some cases, the NMR log includes actuatable regions for examining two-dimensional NMR maps or chain length distributions of the substance corresponding with distinct depths of the substance.