Spatial  Matching Relation of Oil Reservoir Forming Factors and Its Control Effect on Reservoir Formation in Beir Depression

Key words: 
• Beier depression /
• reservoir forming factor /
• spatial matching /
• K1n source rock /
• fracture trap /
• fault trap /
• source fault /

Abstract: Beier Depression is one of second tectonic units in Lake Beier depression, development from the bottom of the bed rock of the Upper Triassic Budate Group(T₃b), the Tongbomiao group（J₂t） of Upper Jurassic, Nantun group(K₁n), Damoguaihe group(K₁d) and Yimin group(K₁y) of Lower Cretaceous, Qingyuangang group(K₁q) Formation of the Yimin group and  the  upper Cretaceous. Combined with results of previous studies, this paper considers source rock, trap, and the source fault are main control factors of hydrocarbon accumulation in Beir depression. Oil and gas mainly from dark mudstone of K₁n and source rock with better conditions, to provide sufficient oil source for hydrocarbon migration and accumulation in Beir depression. Traps are mainly two kinds of type, crack traps and fault traps include fault block, fault seal and fault lithologic traps in Beir depression.The reservoirs of T₃b and K₁d and source rocks of K₁n  located in different layers, faults should be oil migration transporting main pathway.By studies on spatial  matching relation of oil reservoir forming factors in Beier depression K₁n source rock, fracture, fault trap and source fault, it was considered that fracture and fault traps had 4 contact relations with K1n source rocks in space in Beier depression. The first is that fracture traps of Budate group are located at the side of the top of K₁n source rocks. They are connected by T₅ -T₁faults. The second is that K1nfault traps are located in K1n source rocks. They are connected by T₂₃-T₁faults The third is that K1n fault traps are located outside of K1n source rocks. They are connected by sand body connected by T₂₃-T₁ aults. The forth is that K₁d^₂  fault traps are located above of K₁n  source rocks. They are connected by T₂₃-T₁faults .The control effect of space matching relation of 3 reservoir forming factors on oil accumulation and distribution was showed as follows three aspects. ①Distribution of oil reservoir was controlled by the distribution of K₁n source rock. ②Oil reservoirs are all distributed along source faults. The shorter the distance from trap to K₁n source rock, the better it is to form oil reservoir.