塔里木盆地玉北1井原油成因再认识及其意义

Recognition of origin of crude oil from well Yubei 1 in Tarim Basin and its significance

塔里木盆地下古生界含油气系统的油源问题至今仍存在争议。在详细剖析塔里木盆地玉北地区玉北1井原油的分子同位素地球化学特征的基础上,以反演的思路解决该区下古生界含油气系统的油源问题。玉北1井原油作为两期成藏叠加的产物,其两期成藏的油源均为同一套寒武系烃源岩生油高峰期的产物,系不同区域烃源层的埋深差异导致成烃时序的不同。早期成藏的原油由于地层抬升剥蚀遭受严重生物降解,而晚期成藏得以良好保存。尽管原油生物标志化合物组成和分子碳同位素分布特征与盆地内下古生界含油气系统原油具有可对比性,但玉北1井原油中芳基类异戊二烯烃分布指示塔西南下寒武统烃源岩发育的沉积环境与台盆区可能存在一定差异,有待于进一步深入研究。

The oil source of the Lower Paleozoic petroliferous system in the Tarim Basin is still controversial.Based on the detailed analysis of the molecular isotopic geochemistry of the crude oil from well Yubei 1 in the Yubei area of the Tarim Basin,the oil source of the Lower Paleozoic petroliferous system in this area was studied by inversion ideas.The crude oil from well Yubei 1 was the superimposed product of two phases of accumulation,and the oil sources of the two phases were the products of the same set of Cambrian source rocks during the peak period of oil generation.The burial depth of Cambrian source strata in different areas could be the main factor leading to multiple phases of hydrocarbon charging.Crude oil accumulated in the early stage experienced severe biodegradation due to strata uplift and erosion,while oil in the late stage was well preserved.Although the biomarker assemblages and molecular isotopic compositions in the Yubei 1 oil can be generally correlated with oils from the Lower Paleozoic petroleum system in the central Tarim Basin,the distributions of aryl isoprenoids suggested that the depositional environment of the Cambrian source rock in the southern Tarim Basin could be different from that in the central Tarim Basin,which worth a further in-depth study.