Qualitative and Quantitative Analysis of Heavy Crude Oil Samples and Their SARA Fractions with 13C Nuclear Magnetic Resonance

Abstract

Nuclear magnetic resonance (NMR) approaches have unique advantages in the analysis of crude oil because they are non-destructive and provide information on chemical functional groups. Nevertheless, the correctness and effectiveness of NMR techniques for determining saturates, aromatics, resins, and asphaltenes (SARA analysis) without oil fractioning are still not clear. In this work we compared the measurements and analysis of high-resolution 13C NMR spectra in B0 ≈ 16.5 T (NMR frequency of 175 MHz) with the results of SARA fractioning for four various heavy oil samples with viscosities ranging from 100 to 50,000 mPa·s. The presence of all major hydrocarbon components both in crude oil and in each of its fractions was established quantitatively using NMR spectroscopy. Contribution of SARA fractions in the aliphatic (10–60 ppm) and aromatic (110–160 ppm) areas of the 13C NMR spectra were identified. Quantitative fractions of aromatic molecules and oil functional groups were determined. Aromaticity factor and the mean length of the hydrocarbon chain were estimated. The obtained results show the feasibility of 13C NMR spectroscopy for the express analysis of oil from physical properties to the composition of functional groups to follow oil treatment processes.

The Origin, Physicochemical Properties, and Removal Technology of Metallic Porphyrins from Crude Oils

“…Particularly, SARA has been identified as the most used approach, resulting from the good ability to separate asphaltene fractions from others, including the saturated, aromatic, and resin fractions [32][33][34]. This technique is initiated by dissolving the crude oil in dichloromethane solvent, followed by the addition of alumina material, and drying through flowing nitrogen gas [35]. The residue is packed as the stationary phase of the chromatography column and subsequently eluted stepwise using n-hexane:cyclohexane 1:1 v/v, nhexane:toluene 7:3 v/v, carbon tetrachloride:chloroform 7:3 v/v, and acetonitrile:methanol 1:1 v/v to respectively obtain the saturated (A1), aromatic (A2), resin (A3), and asphaltene (A4) fractions of crude oil.…”

Evaluation of Thermo-Viscous Properties of Bitumen Concerning the Chemical Composition

“…Petersen et al [ 5 ] developed a linear combination to describe the bitumen viscosity on the basis of the content of the hetero atoms oxygen, sulfur, and nitrogen. With the development of new analytical techniques, the bitumen composition is expressed by group composition of chemically and structurally related compounds called SARA (Saturates, Aromatics, Resins, Asphaltenes) analyses [ 14 , 15 ].…”

Prediction of the ASTM and TBP distillation curves and specific gravity distribution curve for fuels and petroleum fluids

“…[ 48–52 ] Despite the complexities of the aforementioned methods in predicting distillation curves, the most important problem is their essential need for the composition of petroleum fluids as input data. Although new approaches such as nuclear magnetic resonance (NMR) have been employed in recent years [ 53–55 ] for identifying the unknown nature of petroleum fluids, determining the exact composition of them is really impossible for many oil samples. For this reason, applying the physical bulk properties of petroleum fractions (such as ), which are often measurable and available, would be more efficient in the model development.…”