An Improved Nmr Permeability Model Suitable for Macromolecular Diffusion

Abstract

Summary By combining experiments of macromolecular extraction with Darcy’s law and Poiseuille equation, an improved nuclear magnetic resonance (NMR) permeability model suitable for macromolecular diffusion is obtained. The model includes the physical parameters of movable and irreducible fluid, pore throat ratio rb/rt, tortuosity and the thickness of chemical bond water film and macromolecule film. Scanning electron microscopy(SEM), transmission electron microscopy(TEM), infrared spectroscopy (FTIR) and NMR experiments confirmed the existence of irreducible macromolecules and movable macromolecules. It also explains the reason the T2 spectrum shifts to the left after extraction from different angles. The results show that the proportion of irreducible fluid of samples with NMR characterization can reflect the variation tendency of irreducible macromolecule and water, and the mean value of NMR characterization is 20.6% which is close to the result of chemical extraction 37.38%. By simplifying the pores of extracted samples, the thickness model of irreducible macromolecule and water is established firstly and the total thickness is 1.482nm, 1.585nm，1.674nm，1.834nm. The permeability results of mercury injection experiment are 509.68mD, 472.85mD, 581.89 mD, 555.76 mD are basically the same with the results of the improved NMR permeability model which are 739.34 mD,602.13 mD,527.65 mD,625.93 mD.