Prediction Of Favorable Locations For Hydrocarbon Migration And Accumulation In The Third Member（Ed₃） And First Member（Ed₁） Of Dongying Formation In Nandagang And Beidagang Areas Of Qikou Sag

In shallow layers of hydrocarbon basin,the shallow-buried dark mudstone is immature up to now,and cannot provide oil and gas source for accumulation.If shallow layers are to form reservoirs,their oil and gas can only come from the underlying“transfer station”.The oil and gas in the“transfer station”migrate to shallow layers through regional caprock and transfer faults,then accumulate near transfer faults.As may be inferred from this,the vicinity of shallow transfer faults might be favorable locations for oil and gas exploration.However,actual exploration of shallow oil and gas shows that there are not always oil and gas distributed near shallow transfer faults,and the distribution is mainly controlled by favorable migration and accumulation locations of oil and gas.Therefore,accurate identification of favorable migration and accumulation locations of shallow oil and gas has much guidance significance for shallow oil and gas exploration in hydrocarbon basins.Based on the co-research project“Study on Formation and Evolution of Faults and Their Controlling Effect on Reservoirs in Dagang Exploration Area”finished by Northeast Petroleum University and Petro China Dagang Oilfield Company,Beidagang and Nandagang areas are selected as the research targets.Regional geological data,geochemical data,seismic data,mud logging data,electric logging data,well testing data and oil testing data are used to determine hydrocarbon supply paths by identifying favorable transfer locations of oil and gas of Ed₃ and Ed₁and lateral migration paths of sand bodies,and to determine favorable locations of hydrocarbon migration and accumulation in Ed₃ and Ed₁by superimposed with hydrocarbon supply paths and favorable traps locations.Combined with oil and gas distribution characteristics,this thesis illustrates the controlling effect of favorable migration and accumulation location on oil and gas distribution,and predicts the favorable exploration areas of Ed₃ and Ed₁ of Nandagang and Beidagang areas based on it,providing theoretical evidence for oil and gas exploration in Ed₃ and Ed₁ of Nandagang and Beidagang areas.The achievements and understandings of this study mainly include the following 7aspects:（1）The favorable hydrocarbon transfer locations of Ed₃ shallow layer in Nandagang and Beidagang areas mainly distribute in the east of Beidagang buried-hill structural belt,and a few distribute in the southeast of the studied area.The distribution characteristics of favorable hydrocarbon transfer locations in Ed₁ shallow layer are generally the same as that in Ed₃ shallow layer,but less than that of Ed₃.（2）The lateral migration paths of sand bodies in Ed₃ shallow layer in Nandagang and Beidagang areas are well developed,with totally 25paths developed,mainly distributed in Qikou main sag and secondly in the eastern part of Beidagang buried-hill structural belt,and scattering distributed in other areas.The lateral migration paths of Ed₁ shallow layer are also well developed,with totally 16 paths,mainly distributed in Qikou main sag and secondly in Qibei subsag and Nandagang buried-hill structural belt,and a few in Qibei slope.（3）The oil and gas supply paths of Ed₃ shallow layer in Nandagang and Beidagang areas are well developed,mainly distributed in the east of Beidagang buried-hill structure,secondly in the south of Nandagang buried-hill structural belt and parts of Qikou main sag,and a few in Chengbei fault terrace belt.The distribution characteristics of hydrocarbon supply paths in Ed₁ shallow layer are generally similar with that in Ed₃,except not distributed in Qikou main sag and less number than that in Ed₃.（4）The favorable locations of hydrocarbon traps in Ed₃ shallow layer in Nandagang and Beidagang areas are mainly distributed in the east of Beidagang buried-hill structural belt,and scattering distributed in other areas.The favorable locations of hydrocarbon traps in Ed₁ shallow layer are also mainly distributed in the east of Beidagang buried-hill structural belt,and a few traps are distributed in Nandagang buried-hill structural belt.（5）The favorable locations of Ed₃shallow layer and Ed₁ shallow layer in Nandagang and Beidagang areas are intersection locations between favorable traps and supply paths.The favorable locations of hydrocarbon migration and accumulation in Ed₃ are mainly distributed in the east of Beidagang buried-hill structural belt.The favorable locations of hydrocarbon migration and accumulation in Ed₁shallow layer are mainly distributed in the eastern part of the Beidagang buried-hill structural belt,and a small amount in the southern part of Nandagang buried-hill structural belt.（6）The favorable locations of hydrocarbon migration and accumulation in Ed₃ and Ed₁ shallow layers of Nandagang and Beidagang areas control the hydrocarbon distribution.Oil and gas are mainly distributed in and near the favorable locations of hydrocarbon migration and accumulation,i.e,the oil and gas of Ed₃ shallow layer are mainly distributed in the east of Beidagang buried-hill structural belt,and the oil and gas of Ed₁ shallow layer are mainly distributed in the east of Beidagang buried-hill structural belt and a small amount is distributed in the south of Nandagang buried-hill structural belt.（7）The area near Well Ban64,the south of Well Gang 363,the west of Well Binhai 5 and the north and east of Well Bai8-2 are the favorable areas of further exploration Ed₃ shallow layer.The northeast of Well Qn16X1,the west and east of Well Gangshen 18 and Well Gang 69 are the favorable areas for further exploration of Ed₁ shallow layer.The research has important reference role in guiding the oil and gas exploration of Ed₃and Ed₁ of Dongying Formation in Nandagang and Beidagang areas of Qikou Sag.