The Study On Sedimentary Microfacies Of Fuyu Oil Reservoir, Southern Daqing Placanticline

Aonan researched area, covering parts of Qijiagulong Sag, Qaqing Placanticline, Sanzhao Sag, Chaoyanggou Terrace, is located in the south of Daqing Placanticline in northern Songliao Basin, of which the oil source bed is Qingshankou Formation.The target layer is the Fuyu reservoir of the forth member of Quantou Formation and part of third member of Quantou Formation.Considerable research has been done on the south of placantiline,but the study on aonan area is stil lack of clear understanding mainly including the divison of depositional time unit and the characteristic of sedimentary microfacies distribution.Because of abundant oil&gas resources and lack of systemic understanding on the study of sedimentary microfacies,this paper carries out research on the division and correlation of high resolution stratigraphic sequence and the study of sedimentary microfacies,which provides evidence to realize the sedimentation distribution of this area and theoretical basis on oil&gas further exploration and development.Based on achievements of others in previous research, regional sedimentary background and characteristics of tectonic evolution, under the guide of sequence stratigraphy, logging geology and sedimentology, this paper studies the divison and correlation of stratigraphic sequence of Fuyu oil layer and the divison of sedimentary microfacies of the study area, combined with the seismic, core and logging data. Thus, this study makes the rule of the characteristic of sedimentary microfacies distribution of studied area and evolution clear.The thought and method of division and contrast combining logging and seismic in Fuyu oil layer based on high resolution stratigraphic sequence has been bulit by this study, which completes the study method of sedimentary microfacies.The study finishes the division and correlation of strata of 315 wells in 6 seismic work areas, achieving the Fuyu oil strata division from 5 strata to 12 strata in the south of Daqing Placanticline,which lays the foundation for the sedimentary microfacies division and the understanding of the sedimentary microfacies evolution.The main achievements are:(1) There are five medium term cycles,of which the bottom of FI1, FI3, FII2(moderate continuity, weak amplitude in seismic section) is sedimentary transformation base and the bottom of FI2, FII1(moderate continuity, moderate amplitude in seismic section) is the maximum flooding surface.12 short term cycles interfaces are identified as lithological abrupt interface or flooding surface.(2) The study area mainly develops three kind of sedimentary subfacies including meandering river,delta front,delta plain and four types of sedimentary lithofacies which are block(silty) mudstone,calciferous(muddy) siltstone, tough cross-bedding siltstone, parallel bedding fine sandstone and nineteen sedimentary microfacies.(3) During FII2 and FII1 period in the study area,the provenance is mainly from the northwest and northeast. During FI3 period to FI1 period, the southwest rovenance is gradually developed, strongly extending to north, and north provenance is gradually becoming weak.During FI1 period, the southeastern provenance is gradually developed Research area is the mult-provenance sedimentary system,developing southwest and northwest provenance, locally developing southeast and northeast provenance, which shows a evolution trend that strong in south and weak in north.(4) The FI and FII stratum in the study area is sustainability basin filling sedimentary body, experiencing fluvial, delta plain, delta front subfacies depositional evolution process from bottom to top.he stratum FII2-2 to FI3-1 period is fluvial deposition which has the characterist of curve distribution in south and network distribution in north.During FI2-2 period, the south of the study area mainly developes meandering river deposition, and the northern part develops delta plain deposition.The study area mainly develop delta plain deposition during FI2-1 period, and, during FI1-3 period, develops delta front deposition in north and delta plain deposition in south.From FI1-2 to FI1-1 period, the study area mainly developes delta front deposition.