Fractures Patterns And Its Impact On Shale Gas Enriched In Chongqing Area

Chongqing is a region across Yangtze plate and Qinling orogenic belt,which experienced several tectonic movements,and formed complex superimposed fracture systems by many factors for long.In this paper,We apply seismic and drilling data,high resolution satellite images and field faults and other means to carry out and to analyse fault system features in this area.Through the research,fracture patterns,the fracture system's distribution and the assessment results of shale gas closeness and completeness,which could play an important role for exploring and evaluating the shale gas.1)There are eight structure styles,including box-shaped faulted anticline,dish gentle syncline,symmetric broad syncline,side-relief syncline,closed syncline,the high steep broken folds,inverted syncline and asymmetric gentle dish syncline etc.2)The isolated closed syncline developed attribute to the strong deformation of structures and fold wings strata was severely eroded in SE Chongqing.Simultaneously,most dish gentle syncline developed in the middle of Chongqing because this area lies in front of fold-and-thrust belt and has low strain.3)The fracture distribution is nonuniform in Chongqing obviously through the region's remote sensing interpretation and Wuxi / Qianjiang fine resolution remote sensing interpretation.There are most fractures with high density in NE Chongqing,followed by the SE Chongqing,the worst in middle and west of Chongqing.Most major faults are mainly NE–SW,NW–SE trending in Chongqing except to Northeast where are mainly SN trending.The complicated fractures distribution is caused by different tectonic compression which origins from Indosinian,Yanshanian and Himalayan.Meanwhile,this area,along the sides of Qiyao fault-fold belts,experienced the field stress conversion and formed significant differences of fracture system.4)The 32 blocks of Chongqing area can be divided into three categories on the basis of the structure styles,fracture remote sensing interpretation,fracture characteristics,field joint measurement and analysis of the regional stress field,formation pressure distribution in this region,combined with the formation dip,structural expansion rate,depth index,pressure index and structure closure and integrity parameters: There are better conditions of preservation in Jiaoshiba block,Zhongxian block,Nanchuan block,Beibei-Yongchuan block and so on.Followed by west of Fuling block,Dianjiang block,Hechuang-Rongchang block and so on.The worst is Baima block,Nanyaojie block,Chengkou block and so on.