Selective enhancement of 1H signal from water and oil in porous media at low field with Overhauser DNP

• Published in: Journal of magnetic resonance (1997) 2024-11, Vol.368, p.107793, Article 107793
• Main Authors: Morin, Devin M., Ansaribaranghar, Naser, Nicot, Benjamin, Green, Derrick, Balcom, Bruce.J.
• Format: Article
• Language: English
• Subjects: Hyperpolarization; Imaging; Low-field; Oil; Overhauser; Porous media; Portable MR; Selective enhancement; Water
• ISSN: 1090-7807; 1096-0856; 1096-0856
• DOI: 10.1016/j.jmr.2024.107793

[Display omitted] •Selective enhancement of oil and water in a portable instrument.•A low-field design employing inexpensive ceramic magnets.•Low microwave frequencies permit macroscopic samples.•Discrimination of oil and water in a rock core flooding experiment. In porous media MR studies, discriminating between oil and water presents a challenge because MR lifetimes are often similar and spectra overlap. Low saturations might suggest an experimental strategy of increasing the static field for increased sensitivity, but susceptibility effects are exacerbated at higher field. Overhauser dynamic nuclear polarization, effective at low static field, was employed with water and oil-soluble nitroxide to selectively enhance water and oil signals. We employ a home-built 2 MHz ceramic magnet to achieve selective enhancement of water and oil, in bulk, and in a rock core. For imaging, we employ a 705 kHz ceramic magnet with a 4 gauss/cm constant gradient configuration to image the hyperpolarized signal. A rock core flooding experiment was undertaken to highlight the advantages of Overhauser enhancement. A simple phase cycling technique may be employed to cancel the thermally polarized 1H signal to isolate the enhanced signal of interest.