Major breakthrough in oil-gas exploration has been made in the ultra-deep strata of Shunbei area

Tarim Basin.Following the geochemistry comparison of crude oil and natural gas in the Ordovician Yijianfang Formation in Shunbei area

combined with the analysis of microscopic fluorescence spectrum parameters and fluorescence color

we put forward that the study area has undergone multi-stage hydrocarbon charging

the crude oil charged earlier has experienced biodegradation to a certain degree

while the gas is associated with the crude oil.In addition

through the comparison of crude oil in Shunbei and Shunnan areas in terms of isoprenoid parameters

biomarker compounds and light hydrocarbons in crude oils

we found that the hydrocarbon in Shunbei area is derived from the same source rocks as Shunnan area

that is

from the Cambrian Yurtusi Formation source rocks

and has migrated up to the Ordovician reservoirs along the faults cutting through the Cambrian.The samples collected in Shunbei area were analyzed systematically by fluid inclusion testing

as well as cold cathodoluminescence and fluorescent observations.The results show that there are three stages of oil charging in the late Caledonian

late Hercynian

and late Himalayan respectively

and one-stage gas charging in the late Himalayan.