Structural Characteristics And Evolution Of The Middle And North Part Of Western Sichuan Basin

In recent years,Western Sichuan Basin has shown a good natural gas prospect.Although western Sichuan is rich in seismic and logging data,its petroleum geological conditions are complex due to the characteristics of multi-stage structural evolution and multi-directional structural distribution.At present,the researches on the characteristics of faults and the structures around them are still insufficient,lacking effective and unified understanding.Therefore,the purpose of this study is to clarify the structural characteristics and active mechanism of the faults in the middle and north part of the Western Sichuan Basin by using the existing seismic and logging data.And analyze the hydrocarbon accumulation pattern in the study area,combined with the petroleum geological data in the study area.That may make some contributions to the future oil and gas exploration in western Sichuan.The central and northern regions of the West Sichuan Depression are dominated by thrust structures.The main faults include Guankou fault,Pengxian fault,slip fault in Triassic and Longquanshan fault.There are various structural styles in the area,which are composed of thrust faults,including thrust structures,fault triangles,and thrust shingle fan structures.There are also fold deformations related to thrust faults.The structural development in the study area is characterized by north-south segmentation,east-west zoning and vertical stratification: the structure can be divided into three segments from north to south,with the xinchang structure belt as the middle segment the the tectonic belt north as the north segment and the south as the south segment;from east to west,it can be divided into three zones,which are the trailing edge thrust zone,the transition zone(transfer zone)and the leading edge recoil zone;vertically,the fault system can be divided into shallow slip fault system and deep Sinian-Middle Triassic fault system.Since the sinian period,the western sichuan region has developed seven sets of unconformable interfaces and experienced many evolutionary stages.The foreland basin in Western Sichuan was formed in the Indosinian period,and then reformed and superposed by the Yanshanian and Himalayan tectonic movements.the current tectonic pattern has been formed due to the different regional stress backgrounds controlled alternately by the Songpan-Ganzi fold belt and the Qinling orogenic belt,and the influence of the uneven development of gypsum and the sedimentary lithology of the stratum.The source rocks of marine strata in western Sichuan have favorable conditions,and the multi-stage tectonic movement provides good conditions for the migration and preservation of source rocks.A variety of oil and gas accumulation modes have been formed,including "self generation and storage" and the combination of "self generation and storage" and "lower generation and upper storage"...