Sedimentary And Structural Features Of The Fuyu Oil Layer In The Yuan 13 Block Of The Toutai Oilfield And Theirs Control Over Hydrocarbon Accumulation

The Toutai Oilfield is located in the Chaoyanggou terrace in the central depression of the northern Songliao Basin.The Fuyu oil layer is located in the K1q4 of Cretaceous in Mesozoic.This paper is based on the results of predecessors' research and the core,drilling,well logging,and seismic data of the study area.Using theories of high–resolution sequence stratigraphy,sedimentary petrology and petroleum geology,systematic studies have been conducted on the division of sequence stratigraphy,the study of structural features,the distribution of sedimentary microfacies,and the control of hydrocarbon accumulationThe Fuyu oil layer of the Toutai oilfield is a set of regional lake sediments composed of strata with large changes in water depth and genetic connections between them.On the basis of sequence stratigraphy study,this paper completed division and correlation of 96 wells and divided Fuyu oil layer into 3 oil groups,18 small layers in the method of the technology combined with logging and seismic.Isochronous stratigraphic framework has been established.From the analysis of the fine structure diagram of the top surface of the Fuyu oil layer prepared through processing and interpretation.The fault system in the study area is developed in the NS direction.The fault profile is mainly composed of “y” shape,and the fault-intensive zone is a combination of “horst” combinations.According to the stratum development characteristics and fault configuration of the K1 q in the study area,the area and closure height of reservoirs in this area are small and scattered.Based on the regional sedimentary background of this area,through the core observation and logging phase,combined with the contour map of sandstone thickness and the contour map of sand ratio to ground,the development of a shallow lake delta system in the study area was determined.Source direction is controlled by two water systems,Huaide water system and Baokang water system,and this area developed 2 subfacies(delta plain and delta front)and 8 microfacies.Among them,the water diversion channel and the underwater diversion channel are the main sedimentary microfacies.Comprehensive structural development characteristics and sedimentary microfacies research results have been used to explore the main controlling factors of oil-gas accumulation and oil-gas distribution.The oil-gas accumulation in the study area is controlled by structural and lithology.There are several fault-intensive zones in the area,the reverse normal faults and slope strata are conducive to oil-gas sealing and accumulation,the direction of the sand body of the channel to the tectonic strike is vertical,forming structural-lithologic reservoirs,and the sand body is cut by fault to forming fault-lithologic reservoirs.Through the combination of the two-three type structures and sedimentary microfacies,the foundation for the favorable target area and reservoir evaluation about the study area has been established.