Fractionation of hydrocarbons and NSO-compounds during primary oil migration revealed by high resolution mass spectrometry: Insights from oil trapped in fluid inclusions

The composition of oil trapped in fluid inclusions (FI), occurring mineral cements, can provide valuable insights into migration. Here, FI oils a calcite vein (representing expelled fluids) and source rock (SR) extracts retained bitumen) from the Hosszúhetény Calcareous Marl Formation (HCMF) Mecsek Mountains area Hungary were investigated to assess how organic compounds are fractionated during primary Biomarkers analyzed by gas chromatography–mass spectrometry chromatography-stable carbon isotope ratio mass used demonstrate that had been HCMF marl (calculated vitrinite reflectance ~0.74% Rc). Fourier transform-ion cyclotron resonance-mass then provided polar compound geochemistry, showing O1, N1, N1O1 S1O1 classes preferentially bitumen, while less like aromatic hydrocarbons (HCs) S1 assumed be expelled. Independent class, with higher double bond equivalents (DBEs) enriched bitumen. Thus, besides molecular polarity determined functional groups, size degree aromaticity appear most important factors affecting migration retention behavior petroleum HCs NSO-compounds HCMF. Moreover, enrichment high DBE shorter alkyl chains SR infers shielding effects could have played major role for expulsion