Application of nuclear magnetic resonance to study bituminous oil in the south western Nigeria

Abstract

Heavy bituminous oil is the main source of Nigerian unconventional resources. The resources represent oil sand and bitumen oil forming a belt of bitumen oil covering about 120 km extending from Lagos, Ogun, Ondo and Edo. Huge reserves of the resources are located in the state of Ondo. A nuclear magnetic resonance (NMR) method was used in the research to study bitumen oil in South West Nigeria. The NMR spectroscopy on the nuclei of 1H and 13C uses signals from protons and carbon nuclei, respectively, tetramethylsilane molecules Si(CH3)4. Regions of absorption of aliphatic (7–65 ppm) and aromatic (108–170 ppm) nuclei of carbon atoms are clearly defined in the NMR spectra of 13C of the objects under consideration. Signals of carbon atoms of olefinic fragments make a significant contribution to the last range of spectra of the cores of Nigerian bitumen deposits. An analysis of more known methods of defining the aromatic region of the nuclear magnetic resonance spectrum of 13C showed that for fractions that do not contain condensed cyclic and heteroatomic compounds, the definition of chemical shift subranges (CS) corresponding to aromatic carbon atoms 110–130 ppm not substituted, 130–137 ppm substituted by methyl, another alkyl – and naphthyl substituted – 137–148 ppm is sufficienly reasonable. There are regions of absorption of quaternary carbon atoms bonded to oxygen or nitrogen (148–170 ppm), carbonyl carbon atoms (170–200 ppm), as well as tertiary aromatic carbon atoms, located in the ortho position to the hydroxyl or other oxygen atom (108–118 ppm) in objects containing larger amounts of heteroatoms.

Keywords

• nuclear magnetic resonance method
• tetramethylsilane
• spectrum
• absorption
• oxygen
• hydrogen
• core
• nuclei
• proton
• resources
• bitumen
• oil
• spectroscopy