Oil and Gas Depositional Characteristic and Distribution Law of the Gaotaizi Reservoir in the Western Placanticline,Songliao Basin

By using the high-resolution sequence stratigraphy theory,depositional dynamic analysis,and the cores of 25 wells and 596 well logging data,the Gaotaizi reservoir of the western Placanticline in Songliao basin is divided into 1 long-term base level cycle,5 medium-term base level cycles and 13 short-term base level cycle.This study proposes a new framework of sequences with top layer absent,in which the north and south of the Gaotaizi reservoir are controlled by lifting of syndepositonal structure.Detailed study of sedimentary characteristics recognizes two types of special high-quality sandstone reservoirs,beach bar of shore-shallow lacustrine and fluxoturbidite fan.Our study reveals that the most favorable sandbody is thin channel-mouth bar,sheet sanbody,beach bar and fluxoturbidite fan.However,high-quality thick favorable river sandbody in most northern section of the study area contains no oil,but a large amount of water.Our research found that a variety of types of lithologic reservoirs developed in this area;for example,sand lens reservoir,dumping pinch-out reservoir,fault-lithologic reservoirs and integrated reservoirs.Sandbody development and distribution of lithologic reservoirs are obviously controlled by sedimentary facies.Therefore,the facies controlling theory of depression basin was applied excellently and deepened again in this area.