Advances in low-field nuclear magnetic resonance (NMR) technologies applied for characterization of pore space inside rocks: a critical review

Jian-Chun Guo, Hang-Yu Zhou, Jie Zeng, Kun-Jie Wang, Jie Lai, Yu-Xuan Liu
2020 Petroleum Science  
NMR serves as an important technique for probing rock pore space, such as pore structure characterization, fluid identification, and petrophysical property testing, due to the reusability of cores, convenience in sample processing, and time efficiency in laboratory tests. In practice, NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation. The impetus of this work is to help engineers and researchers
more » ... h petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations. This article first gives a brief description of the development history of relaxation theories and models for porous media. Then, the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented. Meanwhile, limitations and deficiencies of them are summarized. Finally, future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed. List of symbols A Characteristic length (m) A n Proportion of the nth eigenstate (-) B 0 Initial magnetic flux density (T) c 1 H state change probability (-) ⃖� ⃗ D Diffusion coefficient tensor (m 2 /s) D 0 Diffusion coefficient in unrefined environment (m 2 /s) D(t) Effective coefficient (m 2 /s) g Magnetic field gradient (A/m 2 ) 3 Dirac function in 3-D space Surface sink strength (m/s) Δ Susceptibility difference (H/m) n The nth corresponding eigenfunction (-)
doi:10.1007/s12182-020-00488-0 fatcat:ejakyxrporflnhmypomjvtjnre