Basic conditions and main control factors of the hydrocarbon accumulation in the southwestern area of Chuankou Oilfield

The reservoir-seal assemblage composed of Chang 4+5 and Chang 6 of Triassic in the southwestern area of Chuankou Oilfield is near to main hydrocarbon source rock(Chang 7).Because it is in the oriented region of hydrocarbon migration in the generation-expulsion period of a large amount of hydrocarbon,it has good basic conditions of hydrocarbon accumulation.There are mudstone and dense siltstone with back swamp and distributary estuary deposits in the two sides and the upper of oil-bearing sandbodies,and they are composed of updip lithologic shielding and form good lithologic trap.The reservoirs are lithologic reservoirs.The oil reservoirs mainly distribute in the delta plain distributary channel sandbodies in NNE and the delta front subaqueous distributary channel sandbodies in NE.Their hydrocarbon accumulation is mainly controlled by depositional microfacies,high-quality reservoir-seal assemblage and hydrocarbon migration conditions.