Study On The Characteristics Of Exensional-shear Structure And Hydrocarbon Accumulation In The West Of Linnan Subsag

Linnan subsag is the typical extensional-shear basin in Huimin sag,while Linshang and Xiakou broom shaped fault systems are the most distinctive torsional geological structures,and their hydrocarbon-bearing systems are obviously controlled by extensional-shear structure systems.However,the current exploration degree in the western part of the Linnan subsag is relatively low.Therefore,it is important to understand the static and dynamic characteristics of the extensional-shear structure of the study area,which is of great significance for understanding this type of oil and gas accumulation model and carrying out in-depth exploration and development.This paper investigates the research results of extensional-shear structures by domestic and foreign scholars,and then uses the method of fine structure interpretation to identify the faults in the study area and understand its geometric characteristics.Using the analysis method of fault activity,the extensional-shear structures are studied from three aspects:horizontal extension,lateral strike-slip and vertical ascending movement to study the activity of faults,and the intensity and activity of faults are determined.Finally,by anatomizing the typical oil and gas reservoirs in the study area,we can understand the plane and profile distribution characteristics of the reservoirs,summarize the main types of reservoirs,and study the matching relationship between the structures and hydrocarbon accumulation events,and explore the relationship between extensional-shear structure and oil-gas accumulation in the study area.Simultaneously,understand the relationship between the extensional-shear fracture and the main controlling factors of accumulation.According to the research,it is concluded that the fault system can be roughly divided into the northeast-eastern broom-like fault system,the near-East-parallel fault system,the NE-parallel fault system and the plume fault system.The characteristics of its fault activity are from strong to weak from ancient to modern,to weak in Neogene,and stronger in the eastern segment than in the western segment.The law of strikeslip movement has a certain degree of similarity with stretching.This indicates that the early faults are mostly open,and mostly closed during the Neogene,which is not conducive to hydrocarbon migration.The torsional tectonic setting plays an important role in controlling the migration and accumulation of oil and gas,affecting the distribution of oil and gas.The hydrocarbons from the hydrocarbon-bearing depression migrate through the fault along the normal direction of the tectonic line to the high part,and will gather together while encountering the appropriate circle closed.The forward tectonic belts such as the Xiaozhuang-Tangzhuang tectonic belt,the Xinglong Temple and the Shuangfeng tectonic belt in the study area are located in the western part of the hydrocarbon-producing depression in Linnan,which is a favorable pointing area for oil and gas migration and also a favorable accumulation area of oil and gas.