Changing the resonant nucleus by altering the static field, compensation of γ and B0 effects in T2 and T2 measurements of porous media

• Published in: Journal of magnetic resonance (1997) 2024-12, Vol.369, p.107811, Article 107811
• Main Authors: Rajeev, Rheya, Ansaribaranghar, Naser, Aguilera, Andrés Ramírez, Marica, Florea, de Zerón, Laura Romero, Balcom, Bruce J.
• Format: Article
• Language: English
• Subjects: Decay due to diffusion; Gyromagnetic ratio; Magnetic field; Magnetic susceptibility; Multinuclear MR; T2, T2; Variable field magnet
• ISSN: 1090-7807; 1096-0856; 1096-0856
• DOI: 10.1016/j.jmr.2024.107811

[Display omitted] •Multinuclear MR study of 1H, 13C, and 23Na at constant Larmor frequency of 33 MHz.•A variable field superconducting magnet was employed.•For a given f0 = 33.71 MHz, the B0 field for 1H: 0.79 T; 23Na: 2.99 T 13C: 3.15 T.•Similar line widths & inhomogeneous broadening effects observed in T2* measurements.•Similar diffusion through internal field gradient effects observed between nuclei. Multinuclear 1H, 13C, and 23Na magnetic resonance (MR) has many advantages for studying porous media systems containing hydrocarbons and brine. In recent work, we have explored changing the nucleus measured, keeping the Larmor frequency constant, by changing the static magnetic field B0. Increasing the static B0 field distorts the field in the pore space due to susceptibility mismatch between the matrix and pore fluid. Distortion of the magnetic field in the pore space scales with the applied static field. The gradients that result from the spatial variation of the distorted field will also scale with B0. The equations that describe the inhomogeneous broadening in T2* show that the MR result depends on γB0. The diffusion through internal field gradients effect on T2 depends on the product of γ and G, with G depending on B0. Increasing the static field to bring a nucleus with lower γ into resonance at the same frequency will result in the products γB0 and γG being constant, and therefore, inhomogeneous broadening and diffusion attenuation effects in porous media are predicted to be constant. We explore the T2* hypothesis with 23Na and 1H measurements of brine in porous reservoir core plugs. We explore the diffusion through internal field gradients effect hypothesis with 1H and 13C measurements of decane saturated glass beads. The nuclei chosen for study: 1H, 13C, and 23Na are the three most important nuclei for studies of fluids (brine and hydrocarbons) in reservoir core plugs. These three nuclei have a common resonance frequency of 33.7 MHz at static fields of 0.79 T, 3.19 T, and 2.99 T, respectively. All three fields are readily achieved with our variable field superconducting magnet.