An Improved NMR Permeability Model for Macromolecules Flowing in Porous Medium

Resumo

The extraction of macromolecules from nano-self-assembled material can be used as a laboratory model for enhancing oil recovery in reservoirs. By combining Darcy’s law and Poiseuille equation, an improved nuclear magnetic resonance (NMR) permeability model, suitable for macromolecular flow in mesopores is obtained. The calibration coefficients in the Coates equation are expressed in terms of the physical parameters of pore throat ratio r_b/r_t, tortuosity, and thickness of bond film in the improved model. The results show that the proportion of irreducible fluid to total fluid obtained through NMR characterization can reflect the variation tendency of irreducible macromolecule and water. By simplifying the pores of the extracted samples, the thickness model of irreducible macromolecule and water is established with the total thicknesses calculated as 1.482 nm, 1.585 nm, 1.674 nm, and 1.834 nm. The corresponding permeability results obtained from the NMR characterization (K_NMR) are 7.39 mD, 6.02 mD, 5.27 mD, and 6.25 mD. The permeability results obtained from mercury intrusion experiment (K_HG) are 5.10 mD, 4.73 mD, 5.82 mD, and 5.56 mD, and those from the Darcy flow experiment (K_D) are 4.1 mD and 5.19 mD. The absolute deviation between K_NMR and K_HG varies from 0.69 to 2.29 mD, while that between K_NMR and K_D is 1.58 mD. This method can be applied to the enhanced recovery of shale oil.