Tectonic Characteristics And Its Effect On Shale Gas Enrichment In The Regional Of Southeastern Chongqing

Southeastern C hongqing is an important shale gas exploration and development area,The rich organic mud shale in the Ordovician Wufeng Formation and the Silurian Longmaixi Formation is very developed to provide material basis for shale gas reservoirs.To research the characteristics of regional tectonic development and evolution,as well as shale gas geological characteristics and tectonic control of shale gas enrichment are makes great significance to further exploration and development of shale gas.Based on the theory of plate tectonics and according to the background of regional geological structure,mainly uses the traditional geological survey method,combined with tectonic analysis and software simulation,to comprehensive study the geometric characteristics,kinematics characteristics and formation mechanism of the main geological tectonics in the southeastern C hongqing,and discussed the influence of geological structure characteristics on shale gas enrichment,get the following main understanding:(1)The southeastern Chongqing mainly refers to the south-central of the West of Hunan and Hubei fault zone which located on the east of the Q iyueshan fault.The regional target layer has experienced the influence of multi-period tectonic,including Caledonian,Hercynian period,Indosinian period,Yanshan period and Himalayan period.(2)There are nearly 23 large-scale folds including Q iyanshan anticline,and most of them are NE-NNE to linear distribution.There are 17 large-scale faults including Qiyueshan fault,the distribution of small faults in each fracture system is different.The ground joints are mainly oriented in NE direction,N EE direction,NW direction and near NS direction.(3)There are great differences in the spatial distribution of the tectonic structure in the southeast of C hongqing.Since the Mesozoic,the regional tecnotic evolution can be divided into four stages: the uplift in early Indosinian period,the NW-SE squeeze in the late Indosinian-early Yanshan period,the NNW-SSE squeeze in the late Yanshan-early Himalayan period and the NE-SW squeeze in late Himalayan period.The Q inghai-Tibet Plateau movement and the rising of Xuefeng Mountain plays decisive role in the formation of the main structure in the southeastern Chongqing.(4)The buried depth of the Wufeng Formation-Longmaxi Formation in the southeastern Chongqing area is range from 0m to 4500 m,the thickness from Wufeng Formation to the first sub-section of Longmaxi Formation ranged from 0m to 40 m,the total organic matter content in the region ranged from 0.200% to 6.703%,and the average is 2.850%,Ro is ranged from 2.21% to 3.30%.The sedimentation of the target layer has experienced five stages of sedimentary burial stage,the thermal evolution of organic matter has experienced four stages.(5)Compared with the Jiaoshiba area,the tectonic movement in the vast majority of the Southeastern Chongqing is stronger,the fault structure is extremely developed,there is a reverse period,the stratum is uplifted and the target layer is buried shallowly and even exposed to the surface,all of which caused poor preservation conditions,it's only allowed the gas reservoirs formed in the area where with low deformation and less fracture development.In this paper,nine shale gas-rich areas are delineated,six of which are priority areas,with a total area of 2358.08 km2,and the orther three are secondary area,with a total area of 168.12 km2.