Study On Sedimentary Facies Of The3th Member Of Shahejie Formation In M138and Its Adjacent Regions Of Bamianhe Oil Field

This paper takes sequence stratigraphy and sedimentology etc. for a guide, selecting78wells which owning rich data and complete strata, combining the actual production and work in study area, aiming at the station and problems of exploration and exploit, and analyzing the sedimentary facies and its vertical and horizontal evolutionary law by systematical stratum research on fine division and comparison, sedimentary facies and reservoir characteristic in third member of shahejie formation of Bamianhe oilfield M138and adjacent region. Then taking prediction of favorable microfacie and sand body.The study area is located in the south of Bamianhe oilfield, including M138well area and partial region of M14and M22well area, structural location is on the south of Bamianhe south slope belt and Bamianhe nose fracture structurethe. Southeastern boundary is the pinchout line of Paleogene Shahejie formation which is adjacent to Guangrao uplift; northern boundary is the west of M26-laiyangziyanchang, and on the south to M19-X8well, on the west to M113well; eastern boundary is the M138, and from east to west is about12km,the span from north to south is about5km and having exploration area of about60km2. The main oil-bearing is the paleogene third and fourth member of Shahejie Formation, and this paper is focused on the third member of Shahejie Formation.Making use of well logging curve, logging and analyzing assay, and based on principle of "Cycle contrast, hierarchical control, phased constraints", and with form of "full well full coverage", then setting up26union well profiles which controlling the study area, thus realizing the fine stratigraphic correlation of the study area, and constructing stratigraphic framework of third member of Shahejie Formation.Based on description of microscope-based micro-characterization and analysis of scanning electron microscopy of coring wells, combining with systematical study of rock type, color, sedimentary structures, paleontology and logging features, summarizing the facies-makers in study area, the author recognized that Shahejie formation is delta facies and the mainly subfacies are delta front and prodelta subfacies, and further divided them into six microfacies:underwater distributary channel of delta front, underwater distributary Bay, mouth bar, distal bar, sheet sand and predelta mud. The comprehensive research of shahejie formation from the aspects of a single well and sedimentary facies analysis of the association wells and planar distribution of facies can contribute to finding the horizontal and vertical evolution law of sedimentary facies, building sedimentary framework, analyzing the sediment source combining the tectonic setting, stratigraphy and sand distribution law, and establishing sedimentary model.The studies suggest that earlier deposition of third member of shahejie formation coexist delta front and prodelta facies, and the bottom-up, pre-deltaic sediments gradually reduced, and evolved to entire delta front sedimentary later; plane is the main delta front underwater distributary channel sediments which is distributed in most regions of the study area, and interspersed with interdistributary bay; less sand sheet mainly positions in the distributary channel edges, mouth bar and distal bar are scattered in the northeast,the Northwest and northern regions of the study area. And the source of third member of Shahejie formation is originated from Guangrao uplift and bidirectional effect namely southeast and southwest.Main sand body types of third member of Shahejie Formation are delta front subaqueous distributary channel, mouth bar, sheet sand and distal bar, and subaqueous distributary channel sand reservoir properties are superior to other sand. Through the small layer of sand body thickness, reservoir porosity, permeability, exhibition layout, mastered the rule of sand body and physical distribution of3th member, combining with the study area actual reservoir classification standard, and map key small layers of oil reservoir comprehensive evaluation. Among them, the best reservoirs are S3S51and S3S52, close to I-II type reservoir.