NMR Spectroscopy Analysis of Asphaltenes

In crude oil production and processing, asphaltene aggregation followed by precipitation is a major problem for the oil industry as it causes deactivation of catalysts, blocking pipelines, and deposition on the internal surface of the reservoirs, etc. Asphaltenes, a complex mixture of a broad distribution of molecules, consisting of aromatic cores bonded to aliphatics and porphyrin type molecules with heavy metals, are defined based on solubility. Molecular complexity along with varying molecular weight distribution makes asphaltenes a difficult scientific problem to characterize. Over several decades, many researchers have contributed to characterization, analysis, and determination of structural properties of asphaltenes by various analytical techniques. Nuclear magnetic resonance (NMR) spectroscopy and relaxometry are widely applied for characterizing the chemical structures of asphaltenes, interactions between asphaltenes and maltenes, and dynamical behaviors of asphaltenes in bulk and in confined states. The goal of the current review article is to give an insight into various aspects of asphaltene analysis by NMR spectroscopy and relaxometry. Following a short introduction on asphaltenes and theory of NMR technique, recent contributions on asphaltenes by NMR techniques are summarized and presented. Lessons learned and suggestions on possible future work conclude the present review article.