| Under the guidance of classic sequence stratigraphy principles and methods, this study comprehensively used seismic, core, logging, well logging, geochemical analytical data, etc. It established a unified sequence stratigraphic framework from Qingshankou formation to parasequence level including all exploration wells and development wells in the west of Daqing Placanticline north of Songliao Basin and adjacent key areas (Honggang terrace) south of Songliao Basin covered 15 thousand square kilometers. And within the constraints of the sequence framework we deeply analyzed different depositional systems, characteristics of the reservoir, and reservoir forming conditions. And then we forecast a favorable target zone. This study has an important guidance role and reference value on the next step oil-gas exploration and development in this area.It is the first time that regional uniform sequence stratigraphic correlation was carried out to all exploration wells, development wells in the west of Daqing Placanticline north of Songliao Basin and key areas south of Songliao Basin according to the classical principles of sequence stratigraphy. The target zone of Qingshankou formation is divided into three third-order sequences, followed by bottom-up SQ3, SQ4, SQ5. Each of these three sequences is constituted by transgressive system tract and highstand system tract. There is no low stand system tract. So there are six system tract in Qingshankou formation. Where, SQ3 is further divided into seven parasequence, SQ4 divided into five parasequence, SQ5 divided into seven parasequence. And also corresponding relation between sequence formation classification from Qingshankou formation to parasequence level in the west of Daqing Placanticline north of Songliao Basin and oil strata division of oil fields development block was established for the first time,and stratigraphic sedimentary pattern was also established.Data on heavy minerals was firstly applied to the redefinition of deposit source of Qingshankou formation in the west of Daqing Placanticline north of Songliao Basin. From regional deposition background, source analysis and large-scale sedimentary microfacies precise analysis constrained by sequence stratigraphic framework, we can find that, work area mainly affected by the north, northwest and western depositional system. As the northern part of work area is gentle slope and belongs to distant source deposition, delta phase zone width of delta system controlled by the north depositional system is wider than the west (of the steep slopes and is relatively far away from the source of deposition) and the north-west (of the gentle slope and is deposited near the source). Although same belongs to front delta facies zone, and the foregoing reasons, the north depositional system controlled areas sediment smaller grain size, mostly siltstone, shaly siltstone (or a variety of calcium-pelitic siltstone) and mudstone portfolio, and there are lots of ostracods in these lithology, some ostracods formed stratigraphy, and north-west of the lithology of depositional systems is correspondingly more coarse, coarse pebbly, coarse sandstone and fine sandstone, and so on. The whole Taikang uplift belt and the majority districts of the west overlap zone of work area are controlled by the north-west and west depositional systems. Sediment grain size is coarser than the north depositional system. Average sand versus ground value in the north-west and west depositional system controlled zones is higher than the north. Sandbody connectivity is good. However, some areas in the front delta phase zone have been linked together under a unified basin transformation, it is difficult to distinguish; the complexity of the multi-source, multi-sedimentary system evolution caused more difficult on the identification of a unified basin micro-facies. Through the study of sequence and sedimentary characteristics,we can find that during sedimentary period of Qingshankou formation,depocenter in the west of Daqing Placanticline gradually migrate from below to above and from north to south. While the"maximum flooding surface"is a dynamic changing ideal plane,as for large-scale lake basin controlled by different sedimentary system. We established sedimentary model of unified lake basin with different sedimentary system.We defined the relationship between reservoir types developed in the study area and sequence framework by dissecting many typical oil and gas reservoirs. The purpose layer of the study area mainly developed structure, structure-lithology, tiny structure, lithology-fault sheltered,fault-lithology,lithology reservoir, and so on. Reservoirs that structural factors play a leading role can develop in all system tracts; Reservoirs that lithology factors play a leading role mainly develop in transgressive system tract in SQ3; Reservoirs controlled by other factors mostly develop in highstand system tract. Through the study of characteristics of reservoir combination in sequence framework, we learned that source rocks mainly develop in transgressive system tract, reservoirs in highstand system tract, and mudstones developed near maximum flooding surface have good sealing ability for sandstone in transgressive system tract and highstand system tract. Based on the unit of system tract, we analyzed the reservoir forming condition and main controlling factors of Qingshankou formation in the west of Daqing Placanticline. It has a self-sustained self-storage continual hydrocarbon supply for the original reservoir accumulation model and distant source micro-amplitude nasal structure in the west slope, fault lithologic reservoir accumulation model, and oil-migrating fault reservoir accumulation model. Based on the unit of Parasequence, we predicted favorable zone of Qingshankou formation in the west of Daqing Placanticline. Parasequence level sequence stratigraphic framework has a good guidence effection on reservoir prediction.
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