Research On Depositional System Of 3^rd Member Of The Shahejie Formation In The South Of Dongpu Depression

Dongpu depression is a typical oil-bearing and salt-bearing Cenozoic basin, which is located in the southwest of Bohai bay basin. Recently. The basin development is entering into high maturity stage. Most of structural traps have already found, the next target is lithologic-stratigraphic trap. Amount of industrial oil and gas has already found from the third member of shahejie formation in the north of the basin, and the main oil field exists there. However, in the south of the basin, with half area of the whole basin, only baimiao, qiaokou, xinhuo, tangzhuang, machang et al, there are great potential to develop, In the south part of dongpu depression the structure is very complex, and the marker beds are not clear. Lacking of systematic study on sequence stratigraphy and depositional systems becomes an obstacle on lithologic-stratigraphic trap.On the above mentioned questions, with guidance of sequence stratigraphy and reservoir sedimentology theory, using core, dring, logging, seismic data and kinds of testing data, associated with regional geological setting, we carried out sequence stratigraphy division, correlation and depositional system research. Based on point(sigle well) to line(well tie) to surface(plan map) to tract(evolution), depositional system distribubion is illustrated.Comprehensively using core, dring, logging, seismic data et.al, the third member of Shahejie formation is divided into 3 long-term period cycles, 15 mid-term period cycles. Sequence stratigraphy framework in the south part of dongpu depression has been established, and sequence-sediment fill mode is proposed.During the period of 3^rd Shahejie formation sedimentation in dongpu depression, eastern area of the basin is Luxi uplift, western is Neihuang uplift,the south is Lankao uplift, source was supplied from surroundings. Heavy minerals combination and textural maturity and compositional maturity verify the view. The easte is magnetite-white titanium-zircon combination , the south is zircon-garnet-magnenite combination, the west is zircon-tourmaline-magnenite combination.Core of 22 wells, drilling and logging, seismic data are implanted. The third member of Shahejie formation mainly develops delta, fan delta and lacustring system. In the south delta developed, the west developed delta, too. The eastern steep slop develops fan delta. The main fault footwall develops tuibidite fan. In shallow water area of delta front beach and bar developed.In the process of depositional system developing, tectonic movement, climate et.al play great role on basin fill. Associated with the main fault movement period and climate reflected by Paleontology, the factor of depositional system developed and the impact on basin fill are discussed. The main 2^nd order fault moved during the period of lower and middle of 3^rd member of Shahejie formation deposited. While, in the period of upper of 3^rd member of Shahejie formation deposited, the fault moved weakly. On the basis of precedent achievements related, the climate changed from drought,high tempreture to warm damp to drought and warm damp. Tectonic movement, climate and the changes of accommodation and sources supply related are the main factor to basin fill.