Oil–Source Correlation and Secondary Migration Paths in the Triassic Chang 10 of the Yanchang Formation in the Zhidan Area, Ordos Basin, China: Evidence from Biomarkers, Rare Earth Elements, and Carbazole Signatures

The Zhidan area in the Ordos Basin is enriched with unconventional hydrocarbon resources. However, there is a lack of research on oil–source correlation and specific petroleum secondary migration paths in the Chang 10 member, which restricts the exploration and development of petroleum resources in the area. Gas chromatography–mass spectrometry was used to determine the biomarker characteristics of 28 samples and the carbazole ratios of 14 oil sand extracts. Inductively coupled plasma–mass spectrometry was used to determine the rare earth element (REE) compositions of the oil sands and source rock extracts. Oil–source correlation analyses based on biomarkers and REE compositions were cross-validated, and the results showed that the Chang 10 oil in the study area originated from mixed source rocks of the Chang 7 and Chang 9 members, or from separate source rocks in either the Chang 7 or Chang 9 member. Based on the oil–source correlation, 11 secondary migration paths of Chang 10 oil were determined by applying carbazole parameters. The secondary migration path of oil shows that the Zhidan area's eastern part is the preferential oil accumulation area.