The Characteristics Of Cenozoic Fault System In The Eastern Bonan And Its Control On Sedimentation

In recent years,China has carried out a lot of exploration work for offshore oil and natural gas.A large number of oil and natural gas reservoirs have been found in China's territorial waters.The bohai sea,Donghai sea,Nanhai sea and other basins are rich in oil and natural gas reserves.Among them,the Bohai sea area is the most potential petroleum basin in China's marginal sea basin.The exploration practice for many years shows that the potential of subtle reservoirs,especially the structure-lithologic complex reservoirs,is relatively large.The extensional tectonic pattern in bohai bay basin was developed by the superposition of multi-stage fault tectonics.It is of great significance to study the development,evolution and genetic mechanism of faults for the exploration of complex reservoirs in this area.This paper takes the KL11₁2 work area in the east of Laizhouwan sag as the study object.On the basis of previous studies,combined with structural geology,seismic sedimentology,sequence stratigraphy,sedimentology,and comprehensive analysis of 3d seismic,drilling and logging data,the structure characteristics of the Cenozoic fault in the studied area were analyzed,and the fracture system on the control action of sedimentary system and reservoir distribution in the study area.The Cenozoic sequence stratigraphic framework in the east of Laizhouwan sag was constructed by sorting out and analyzing the drilling and logging data and combining with the fine interpretation and tracking of 3d seismic data.The Paleogene identified three secondary sequences and eight tertiary sequences.The Neogene identified two secondary sequences and five tertiary sequences.By observing the properties of the sequence interface and analyzing the seismic reflection characteristics in the sequence,the evolution process and characteristics of the faults in the study area are analyzed.The fracture is explained in three-dimensional seismic profile.Through observation,it is found that the faults in the working area are mainly divided into simple shovel type,simple "Y" type,compound "Y" type,fault-step type combination and negative flower type.Through the analysis of plane assemblage in the research area,the fault mainly presents east-west or NE-SW distribution,and mainly presents as comb,wild goose,feather and parallel.Through the statistics and analysis of the synsedimentary faults in the study area,it is found that the synsedimentary faults in the Paleogene series have been active for two periods and gradually weakened to almost stop.The most active periods of synsedimentary faults were the lower sha-san period and the eastern sha-san period.The tectonic activity in the Neogene study area is relatively weak,so the development of synsedimentary faults is not obvious,but it is still of great significance to study the fault system in this period.There is an NNE strike-slip fault zone which is a branch of Tanlu fault zone in the study area.The fault developed in the early Paleogene.Activity intensity reached its peak in Shasan-Dongying formation.The three strike-slip faults show the combination of lateral joints in the plane.The porpoise effect and the ribbon effect can be observed in the section.The strike-slip fault zone is of great significance to the formation of the sedimentary system and also has a certain control effect on the distribution of oil reservoirs.The fault system in the study area has a good control effect on the sequence sedimentary system and landform.The east-west fault F1 separates Laizhouwan sag from the Laibei low uplift.The strike-slip fault zone is located in the interlacing zone of rivers and lakes in Neogene.It has obvious influence on the formation of sedimentary facies and the injection of eastern provenance.