Study On Sequence Stratigraphy And Sedimentary Systerm Of Nenjiang Formation In Northern Songliao Basin

On the basis of the study on 3D projects of the Northern part of Songliao Basin, this project sets up the high frequency sequence stratigraphic framework with the application of the theories of sequence stratigraphy and sedimentology. Helped by seismic data, borehole log, logging curves and cores, detailed research and analysis on the sequence stratigraphical framework, depositional system, evolution of the Nenjiang Formation in the north Songliao Basin have been carried out in the paper.One basic third sequence and one complex third sequence are divided in Nenjiang Formation. Six fourth sequence boundaries T₀₆¹, T₀₆², T₀₆³, T₀₆⁴, T₀₆⁵, T₀₆⁶ and seven fourth sequences are divided in No.2&3 Members of Nenjiang Formation. T₀₆ fourth sequence boundary is proposed to have the characteristic with depositional unconformity.Based on the structural framework and sequence stratigraphical framework, the features of sedimentary facies and sand dispersed system in different system tracts are revealed the pattern of source and summarized depositional evolution with the application of a research method of seismic sedimentology. Because of the elevation of eastern Songliao Basin and the change of paleogeographical framework, source direction changed greatly, from south-north to east-west, and fast moved forward the lake with the rapid elevation after large-scale transgression in the late period of No.2 Member of the Nenjiang Formation. The depositional period of Nenjiang Formation in the Songliao Basin is the shrinking period of depression basin. With the evolution of Songliao Basin, paleogeographical framework of different areas changed in the different periods.All in all, river facies, meandering river delta, braided river delta, lake have been distinguished in the area. The depositional evolution of Nenjiang Formation in the basin is divided into two stages, lacustrine expansion of No.1&2. Member of the Nenjiang Formation and lacustrine regression of No.3, 4, 5 Member of the Nenjiang Formation. Favorable exploration layers and zones are predicted based on geological comprehensive analysis. The favorable exploration areas are Da'an-Xinzhan, Puxi, Longhupao, west Lamadian for Heidimiao oil layer of No.3&4 Member of Nenjiang Formation, slump turbidite fans of Daqing anticlines for No.2 Member of Nenjiang Formation, S0 channels of Qijia-Changyuan-Sanzhao area for No.1 Member of Nenjiang Formation.