Study On The Depositional Microfacies Of Fuyang Oil Bed In Gaotaizi Area Of Daqing Placanticline

Gaotaizi zone is located in the south of Daqing Placanticline. Fuyang oil bed that is lower cretaceous Quan3 and Quan4 member has such character as bad lateral connectivity, Bad Petrophysical properties and low oil-abundance. Depending on the structural and sedimentary characteristic, applying the research approach of from point(well) to line(section),from line to face(surface)and from face to field(time and space),in this paper, the distribution and evolution law of depositional microfacies was analyzed and the character of reservoir sand body of target stratum was ascertained.According to observing and describing of cores of 45 wells in study region, lithology type, depositional structure is recognized and lithoface is divided.At the same time, combining well logging with logging, many kinds of log facies and the association are divided. By combining well with seism, depending on the division and correlation of high resolution sequence stratigraphy in Fuyang oil bed, the isochronous stratum framework was established. On the base of the division of sedimentary microfacise and interpretation of seism, applying the thought of the multi-component analysis of seismic attributes and transforming the attributes to sedimentary parameter, sand ratio and sand depth map is drawed. At last combining cores and well logging characters, applying the principle of facies sequence, the distribution of depositional microfacies of middle cycle stratum is ascertained.The study indicated that Fuyang oil bed of this research zone formed at the time of sediment filling during the course of Songliao Basin depression.The rate of descending was high and the weather was dry or semiarid. Stream with many material inpour south lake zone from north-west direction along low gradient and long axes of the depositional basin. Flat and widen topography,shallow lake water and wake wave energy,target stratum belongs to the depositional system of stream dominated shallow-lacustrine delta. Quan3 is delta plain subfacies and Quan4 is delta front,including five kinds of microfacies,distributary channel, natural levee, bay between distributary channel, crevasse spray, mouth bar. The distrubutary channel sand developed most and it is favorable reservoir, the mouth bar did not develop.During the flooding course from Quan3 to Quan4 member,with the stream of lake pushing from south-east to north-west direction. depositional situation formed which meandering stream is located in north and anastomosing river south.At the same time ,it evolve from the direction of area of meandering stream shrinking and area of anastomosing river expanding.