NMRD Method for Quantitative Wettability in Porous Media
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Solution Overview
Problem
Current methods for determining wettability and other parameters of porous media are limited, particularly in providing a quantitative, in situ measurement of fluid dynamics within these media, which is crucial for oil recovery and understanding molecular interactions in confined environments.
Innovation Solution
The method employs nuclear magnetic relaxation dispersion (NMRD) to measure proton spin-lattice relaxation rates as a function of magnetic field strength, allowing for the determination of wettability and other parameters by analyzing the ratio of surface residence time to translational correlation time, and using dispersion curves to derive information about pore size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If macroscopic measurements such as contact angles and capillary pressure curves are used to measure wettability, then the measurement method is simple and widely applicable, but the measurement precision and quantitative capability for in situ fluid dynamics are insufficient
Solution Approach 1:
The patent replaces macroscopic mechanical measurement methods (contact angle measurement, capillary pressure curves) with nuclear magnetic resonance (NMR) physics-based measurement. This substitution enables quantitative in situ measurement of wettability parameters by measuring proton spin-lattice relaxation rates and analyzing molecular dynamics in porous media, thereby improving measurement precision while providing direct insight into fluid behavior at the pore scale
Solution Approach 2:
The patent changes the measurement parameter from macroscopic geometric parameters (contact angle) to microscopic magnetic relaxation parameters (spin-lattice relaxation rate 1/T1). By measuring the frequency-dependent relaxation rates and analyzing the molecular dynamics parameters (surface residence time, translational correlation time), the patent achieves quantitative wettability characterization that reflects actual fluid dynamics in porous media
2Loss of information
If NMR relaxation times (T1 and T2) are measured to characterize porous media, then molecular dynamics information is obtained, but direct quantitative wettability determination is not provided
Solution Approach 1:
The patent segments the NMR relaxation measurement into frequency-dependent components by performing measurements at multiple Larmor frequencies. This segmentation of the relaxation rate data allows separation of different molecular dynamics contributions (surface residence time effects vs. bulk diffusion effects), enabling extraction of specific wettability-related parameters from the overall relaxation behavior
Solution Approach 2:
The patent adds the frequency dimension to the traditional single-point T1 measurement by measuring spin-lattice relaxation rates across a range of Larmor frequencies. This dimensional expansion transforms the measurement from a single relaxation time value to a dispersion curve (1/T1 vs. frequency), which contains additional information about molecular dynamics and enables quantitative wettability determination
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 enables direct, quantitative assessment of wettability and fluid dynamics within porous media, distinguishing between wetting and non-wetting fluids and providing insights into pore characteristics, thereby enhancing the understanding and management of fluid flow in oil recovery processes.
Implementation Method 1
In an externally applied static magnetic field, the spins of nuclei align themselves along the direction of the static field
Implementation Method 2
This equilibrium situation can be disturbed by a pulse of an oscillating magnetic field (e. g., a radio frequency (rf) pulse) that tips the spins away from the static field direction
Implementation Method 3
the spins precess around the direction of the static field at the Larmor frequency, given by ω0=γ*B0
Implementation Method 4
the spins return to the equilibrium direction according to a decay time, T1, which is known as the spin-lattice or longitudinal relaxation time
Implementation Method 5
the spins precess at slightly different frequencies, so that the transverse magnetization dephases with a relaxation time constant T2
Data Source
AI summary
A nuclear magnetic resonance relaxation dispersion method to determine the wettability and other parameters of a fluid in a porous medium such as in an earth formation is provided. The method includes the steps of measuring the spin-lattice relaxation time T1 of the fluid in the porous medium at varying polarizing magnetic field strengths or nuclear Larmor frequencies; and determining whether the values of T1 at varying Larmor frequencies follow a dispersion curve that is characteristic of the parameter of the fluid in the porous medium to be determined.