Study On Development Features Of Qianbei Fault Belt And Its Controlling Effects On Sedimentary Features

Qianjiang depression is a fruitful depression for oil exploration where had deposited huge saline sedimentary called by Qianjiang formation that generated the four series of hydrocarbon zone and combined with the north Qianbei boundary fault to develop the most reservoir type in this region.The length of this fault is about 8000 m.The tectonic movement had separated the Qianjiang depression from the whole sag which contained Jingmen depression,Lexiangguan uplift,Hanshui depression as two parts at the deposited period of Qianjiang formation and the fault controlling deposited of Qianjiang formation.Although the area where located in the north of Qianjiang depression has been explored for many years,it still has half of oil resource for second exploration.Nowadays,the main prospecting forces on subtle oil reservoir for it found some reservoirs.It still obscures that the internal structure of Qianbei fault belt,which caused many different theories about original of “Jingsha Red Wall” located in Qianbei fault belt.Therefore,study on filling sequence and evolution model of Qianjiang depression,especially on controlling of faults on sedimentation in Qianbei fault belt is necessary and important for exploration.This paper on the basis theory of structural geology,sequence stratigraphy,basin analysis and application of the theory of sedimentology and applied seismic data from last time processing.Fine interpreting for this seismic cub and accuracy caving the structure of Qianbei fault belt,it has comprehensive and systematic summarized genetic mechanism and growth distribution laws of Qianbei fault belt.According to the characteristic of fault belt,it has divided the evolution stag into three parts.Besides,it has also recovered depth of disintegration formation,which conducted the development of fault analysis.The discrepancy can be found along the trend of fault belt by balanced profiles which based on typical structure.Moreover,it has summarized the spatial characteristic of Qianbei fault belt through distributing feature on flat and vertical.The activity stage of Qianbei fault was divided into two main sedimentary period,compared with two phase of the sedimentary characteristics,it analyzed the controlling effect of faults on sedimentation that includes three parts below:(1)The Qianbei fault belt pull-apart after first strike-slip and was the associated fault of Tan-Lu fault zone.A series of basin created by a tension force in east China at Cenozoic,as Jianghan basin is one of those basin.Qianbei fault belt triggered by Tan-Lu fault zone and rifted as the boundary fault which controlled Qianjiang formation deposition.(2)The controlling effects of Qianbei fault belt are stronger in east than it in west and earlier than later.The settling volume in east is four times than it in west,this feature obviously exist in Eq4 low formation.The settling rate above Eq2 formation is higher than it below Eq2 formation.(3)”Red Walls”descended from Jingsha formation by shear action of Qianbei fault during the depression.Differential sedimentation and interaction of faults activity molded the particularly style inside.At the same time it also received the following four points:(1)The genetic and evolution of Jianghan basin are strictly controlled by regional tectonic background and evolution.Qianjiang depression is a product produced by multiphase tectonic movement inside of Jianghan basin.(2)Qianbei fault belt has a variety of fault tectonic styles and sublevel faults complicated structure which strictly controlled deposit.Fault block mainly generated in west and fault-nose mostly found in east.The styles of fault group are parallel type,nearly parallel type,the echelon,the oblique type on flat andladder fault,reverse ladder fault,“Y” type,reverse Y” type,graben,horst on vertical.(3)Qianbei fault belt moved in many stages and cycles.Qianbei boundary faults were active during the early time,inside sublevel faults were vibrant in the middle time and the boundary faults aroused again at last time,some of faults were still slipping during the time of Guanghuasi formation deposited.(4)Qianjiang formation sedimentary stage can be divided into rift and sag stages.The Qianjiang formation where located in present depression deposited from lowstand system tract in rift stage.In sag stage,sedimentary expand out of present depression which deposited highstand systems tract.In this paper,based on the research of the Qianbei fault belt development,it realized that Qianjiang depression is a product produced by multiphase tectonic movement inside of Jianghan basin.It also known that “Red Wall” had the same history as Qianjiang depression within Jianghan basin.It would do some help for advice for reservoir exploration through the controlling effects of fault movement analysis.