Crude Oil Analysis by Low-Field NMR Relaxometry

Reliable characterization of crude oil properties remains a central task in petroleum research and industry. Conventional methods established by ASTM standards are time-consuming and rely on toxic reagents, which have motivated the development of alternative approaches. Low-field nuclear magnetic resonance (LF-NMR) has emerged as one such method, offering low cost, simple operation, and minimal sample preparation. In this review, we summarize recent progress in applying LF-NMR relaxometry to crude oils and their fractions. Particular attention is given to correlations between relaxation times, viscosity, and density, and to the use of machine learning techniques to improve the prediction of these parameters. Applications to crude oil emulsions are also considered, where LF-NMR provides insights into droplet size distributions, phase composition, and stability. Finally, advances in SARA analysis are discussed, including new approaches that extend LF-NMR characterization to complex water-oil systems. Together, these studies demonstrate that LF-NMR relaxometry is a versatile tool with strong potential for rapid, nondestructive analysis, contributing to both laboratory characterization and practical flow assurance in petroleum production.