Objective‌ and Methods As the characteristics of large resource potential, low exploration degree and external slope accumulation of Wuerhe Formation in the northeast slope of Dongdaohaizi Sag, Junggar Basin.Comprehensively using the data of geochemistry, reservoir thin section observation and oil-water characteristics to study the characteristics of hydrocarbon accumulation.

Results The results show that the Lower Permian Pingdiquan Formation is an effective source rock with the total organic carbon content up to 2.5%. The organic matter type is II₁-III, and gas generation gradually changes from the center of the depression to oil generation from the slope area. The reservoir rocks of Upper Wuerhe Formation are mainly fan-delta conglomerate, and the reservoir physical property is generally poor. The development of fractures is the key factor affecting the reservoir quality, which is a typical "pore-fracture dual control" reservoir. The regional cap beds of the 3rd member and the local cap beds of the 2nd member combined with the relatively stable structure of the late stage created a good sealing condition for oil and gas reservoirs. The accumulation mode is that the oil and gas generated from the source rocks of Pingdiquan Formation migrated vertically through faults or micro-fractures, forming lithologic and fault-lithologic reservoirs in the glutenite of Upper Wuerhe Formation, which has the characteristics of "one sand and one reservoir".

Conclusion Under the condition of near-source accumulation and large area of reservoir distribution, fan delta front facies sandstone development area adjacent to hydrocarbon generation sag is the most favorable exploration area.