Abstract:

Fuyu reservoir of Sanzhao depression in Songliao basin is a typical down-migration accumulation in syncline of large depressions.Applying the high-resolution sequence stratigraphy theory，analyzing different scales of base-level cycles and stacking patterns with sediment dynamics，based on 11 well cores and loggings of 825 wells，Fuyu reservoir were classified into 1 long-term level cycle，4 mid-term level cycles and 35 short-term level cycles，proposed sequence framework that is regression followed by transgression.The sediment characteristic of short-cycle reservoir suggests that Fuyu reservoir is mainly affected by two sources，the northern Baiquan-Qinggang and the southwest Baokang，which meet around Xujiaweizi then flow to the east，Fuyu reservoir develops typical sedimental system of shallow water delta that controlled by rivers，and distributary channels are main microfacies type. Faults analysis shows that T₂ has the features of intensive belts in plane and flower-like in section，and the oil-sources faults that petroleum accumulation period successively active are main boundary faults of concentrated ribbons. At the end of Mingshui Formation, hydrocarbon generated by Qingshankou source rocks migrates down along open boundary faults of concentrated ribbons at the force of overpressure，then short lateral-migration  along channel sand, finally accumulated on horsts and fault terraces of the uplifted side of both sides，but in the intensive fault zone，most of the units are grabens，so it is not good for accumulation. Based on of the accumulation model，47 hydrocarbon rich target area were depicted，50 million tons of geological reserves are submitted，which gave a clear direction in the exploration and development for the Fuyu Formation in Songliao basin.

Key words: Fuyu Formation, sedimentary characteristic, accumulation model, Sanzhao depression, petroleum gas