The Chunfeng oilfield is located in the Chepaizi uplift of the northwestern margin of Junggar Basin.The heavy oil reservoir is characterized by shallow burial

multiple oil-bearing layers

high oil density and viscosity.The biomarkers generally experienced strong degradation

making it hard to perform oil-source correlation and study of oil accumulation.In this paper

we used experimental methods to analyze fluid inclusion's composition

optical characteristics

occurrence features

homogenization temperature and salinity

performed oil-source correlation

and studied the accumulation period and process.The results show that the heavy oil was mainly sourced from the Permian source rocks in the Changji Depression

and the oil has experienced a slight biodegradation before accumulation and strong degradation later.Late charging also occurs in some wellblocks.At the end of Triassic

the Mid-Lower Permian source rocks had entered into peak oil generation and the oil generated from the Permian migrated to and accumulated in the Cheguai faulted belt.The tectonic movement during the end of Cretaceous to Paleogene destroyed and reconstructed the reservoir in the Cheguai faulted belt

and the hydrocarbons migrated to the Chepaizi uplift and accumulated in the Jurassic and Cretaceous reservoirs.Because of the poor preservation conditions

the oil commonly experienced strong biodegradation and was turned into heavy oil.Since the Neogene

the tectonic movement further adjusted the reservoirs in the Cheguai faulted belt

oil and gas migrated to Chepaizi uplift and accumulated in the favorable traps in Chunfeng oilfield and was biodegraded later into heavy oil reservoir.