Characterization of heteroatom distributions in the polar fraction of North Sea oils using high-resolution mass spectrometry

Abstract Resins are a sub-fraction of crude oil consisting of heteroatom-containing polar compounds. These species are of key importance in oil recovery, oil fluid thermodynamic properties, refining processes and for the environmental impact of petroleum production. Due to the inherent complexity of crude oil, little is known of the absolute molecular structure of these compounds. Here we show how a combination of separation science and mass spectrometry reveal the compositional space of resins isolated from Danish North Sea crudes. By employing spectral stitching mass spectrometry, we resolve over 15,000 unique peaks, an increase of 50% compared to broadband acquisition. The results indicate that the dominant component of North Sea resins are basic nitrogencontaining compounds with small to medium sized aromatic cores. Using chemometric data treatment it becomes evident that each field displays unique profiles, and that these fractions can be used for oil-oil and oil-source correlations. Further, a more detailed knowledge of their composition will allow us to gain a better understanding of the interactions between resins, hydrocarbons and reservoir rock material. Improved understanding of rock-fluid and fluid-fluid interactions is key for development and understanding of improved recovery mechanisms for tight chalk reservoirs.