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

矿物胶结物中的流体包裹体 (FI) 中的油成分可以为石油运移提供有价值的见解。在这里，研究了匈牙利 Mecsek 山区 Hosszúhetény 钙质泥灰岩组 (HCMF) 中方解石脉中的 FI 油（代表排出的流体）和烃源岩 (SR) 提取物（代表保留的沥青），以评估有机化合物是如何分馏的在初次迁移期间。通过气相色谱-质谱法和气相色谱-稳定碳同位素比质谱法分析的生物标志物用于证明 FI 油已从 HCMF 泥灰​​岩中排出（计算的镜质体反射率为 ~0.74% Rc）。傅里叶变换离子回旋共振质谱然后提供了对极性化合物地球化学的见解，表明 O₁、 N ₁、 N ₁ O ₁和 S ₁ O ₁化合物类优先保留在烃源岩沥青中，而极性较小的化合物如芳烃 (HC) 和 S ₁假设化合物被优先排出。与化合物类别无关，具有较高双键当量 (DBE) 的化合物在滞留烃源岩沥青中富集。因此，除了由官能团决定的分子极性外，分子大小和芳香度似乎是影响石油 HCs 和 NSO 化合物在 HCMF 中迁移和保留行为的最重要因素。此外，SR 提取物中具有较短烷基链的高 DBE 化合物的富集表明，屏蔽效应可能在初级油运移过程中对化合物的保留和排出起主要作用。