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

Abstract

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.