Modeling two-dimensional magnetic resonance measurements in coupled pore systems

Area of Science:

• Geophysics
• Materials Science
• Nuclear Magnetic Resonance Spectroscopy

Background:

• Nuclear Magnetic Resonance (NMR) is a powerful technique for probing porous materials.
• Understanding relaxation and diffusion processes is crucial for interpreting NMR data in complex systems.
• The micrograin consolidation (μGC) model represents a simplified system with mixed porosity.

Purpose of the Study:

• To perform numerical simulations of a two-dimensional (2D) T2-storage-T2 NMR process.
• To compare simulation results with predictions from the analytic two-site exchange model.
• To identify limitations of the two-site exchange model in describing NMR relaxation and diffusion in mixed porosity systems.

Main Methods:

• Numerical simulations of a 2D T2-storage-T2 NMR experiment were conducted.
• The micrograin consolidation (μGC) model was used to represent a mixed porosity system.
• Input parameters for the analytic two-site exchange model were independently established for comparison.

Main Results:

• Qualitative and semiquantitative agreement was observed between the numerical simulations and the two-site model.
• Specific discrepancies were identified where the two-site model failed to accurately capture relaxation and diffusion effects.
• Failures were particularly noted when magnetization gradients formed within larger pores during the initial 2D NMR process phase.

Conclusions:

• The analytic two-site exchange model has limitations in accurately describing NMR relaxation and diffusion in systems with complex pore structures.
• The assumption of spatially uniform magnetization within subpore systems in the two-site model restricts its applicability.
• Advanced simulation methods are necessary to accurately model NMR behavior in heterogeneous porous media like μGC.