Research On Subtle Stratigraphic Formwork And Sedimentary Microfacies Of The Fuyu Oil-bearing Layer In Zhou 201 Area, Daqing Oil Field

Daqing placanticline and around areas of Fuyang oil-bearing layer is the first region where will provide reserves in recently, Fuyang oil-bearing layer belongs to low depositional cycle of large depression stage in Songliao basin, its depositional environment belongs to shallow lacustrine-delta system mainly. The major problem in this areas is that the geological condition is complicated. Distributary channel sand bodies is controlled by poly-provenience, it interchanges in vertical and horizontal, takes on strip, has small scale, thin thickness, bad physical properties and low produce. Stratigraphic lithologic composition change frequently in transverse direction, caused poor development effects. The strata is deep in subterranean, strong in diagenesis and littlie difference in wave impedance, its seismic reflect feature is not clear. Lithologic trap of sand bodies is common, form lithologic and fault-lithologic oil-gas pool mainly.The main exploration target is predicting permeable reservoirs, looking for and identifying channel sand bodies that is favorable to forming oil-gas pool. Owing to Fuyang oil-bearing layer special geological condition, it is rather difficulty to identify channel sand bodies.Therefore it is necessary for us to develop technology of identifying channel sand bodies of Fuyang oil-bearing layer with geology and seism together to tackle key problem. The Zhou 201 site is chose as experiment areas, under control of dense well array, which will be studied deeply from high resolution sequence formwork to sedimentary facies time-space evolutionary rule of Fuyang oil-bearing layer. Making clear types of sand body, shape of its geometry and characteristics of its distribution in space, will provide a precise geological model for Fuyang oil-bearing layer channel sand bodies seismic identifying, form a effective and utility Fuyang oil-bearing layer channel sand bodies identifying methods and technology to guide exploration deployment.Various kinds of comprehensive theories and methods is applied in this paper, such as sequence, high resolution sequence, sedimentology, seismic stratigraphy, petroleum geology. Beginning with study of sedimentary microfacis, parasequence stratigraphic division and correlation, Fuyu oil-bearing layer sedimentary characteristics, sequence formwork, sedimentary facies belts rules of distribution in vertical and horizontal have been mainly studied. Through the above study, stratigraphic subtle formwork has been established, sedimentary facies evolutional rules have been known, that provided a precise geological model for Fuyang oil-bearing layer channel sand bodies seismic identifying.Through this comprehensive study, it has been determined that Fuyang oil-bearing layer belongs to shallow lacustrine-delta facies and shallow lacustrine facies, the main kinds of channel include proximal and distal meandering distributary channel, proximal and distal low-sinuosity distributary channel , proximal and distal straight distributary channel and subaqueous distributary channel. The distributary channel sand developed most, and it is favorable reservoir. The hannel sand body is thin in thickness, fine in grain. The channel width is 150～500m. Upward water deepen parasequence is existent in Fuyu oil-bearing layer shallow lake, it is result of river and lake working together, flooding and submerging of lake water cause drowned valley, form distal distributary channel .Quan4 member Fuyu oil-bearing layer is a third-grade climate sequence, the boundary between Quan4 member and Quan3 member is sequence boundary below, T2 reflect layer is sequence boundary above. This sequence include both trangressive systems tract (TST) down and forced regressive margin systems tract (FRMST). TST develop distal and proximal meandering river deposit early, and distal and proximal low-sinuosity river deposit late.The muddy rock microfacies in Quan4 member Fuyu oil-bearing layer is large development, and often contain sand that belong to overwater and subaqueous distributary channel, natural levee, crevasse as well as mouth bar. Consequently, form good reservoir and seal assemblage, which is favorable for the formation of lithologic trap hydrocarbon reservoir.Clear understanding of the evolution features of sedimentary facies, law of sequence evolutioin and distribution rules of sand body microfacies is meaningful to channel sand body seismic identifying, reservoir prediction, reserve estimation and lithologic trap oil-gas pool discovery.