The Regional Tectonic Characteristic Of Northeast Sichuan Basin And Its Control To Oil And Gas Reseroir

Northeast Regional Of Sichuan lies in the north of Qingling and Yangzi Block,abus Longmen mountain thrust nappe tectonics in west, abuts South China fold systerm in Southeast. According to tectonics deformation, evolution characters and geological conditions, we studied the relationship of between Daba mountain thrust nappe and the formation of oil-gas. Daba mountain arc thrust nappe tectonics lie in the boundary of Sichuan province, Shanxi province and Hubei province, which separate Qinling and Yangzi block. There are Hannan block in the northwest and Huangling block in the east. Its extended direction is east-northeast in the northwest area, east-west in the middle area and east-northeast in the southeast area,being a southwestward arc made up of many thrust nappes. The main characters of Daba mountain thrust nappe tectonics are a series of arcual fractures and drapes among folds.Based on Chengkou-Fangxian fracture and Zhenba-Jiming temple fracture from north-west to west-south, there are three conformation zones as follows: north Dabas mountain nappe thrust folds,south Daba mountain nappe front thrust folds and south Daba mountain nappe front detachment folds.According to the involved periods of nappe tectonics,the relationship of strta nappe before and after, space and complex relationship in different nappe tectonics periods, we devided Daba mountain tectonics into yingzi period, yangshan period and xishan period.In short,Daba mountain arcual thrust nappes have different cause of formation and complex tectonics of various period. Combing the basin paleogeography and the evolution of structure, the basin evolutions were devided into craton depression in Early Palaeozoic, craton depression in Late Palaeozoic, foreland basin in Mosozoic, Land collision from Triassic period to Sinian period, and the stage of structure evolution in Mesozoic. By the analysis to the chronogenesis of NE,NW,EW structure in the Northeast of Sishuan ,and the compound analogy of Daba mountain structure belt with West Xiang'E structure belt, three stages which were Indo-chinese stage, Yanshan stage and Himalayan stage could be separated in the studied area. By statistics and analysis of fold axis,lines and conjugate joints in structures of every stages, the paleotectonic stress fields in Indo-chinese stage, Yanshan stage and Himalayan stage were resumed. Based on anatomizing known oil-gas fields in the field investigation, discussed systermical faults ,unconformity ,tectonic facies and its oil-gas-controlling. And researched source-reservoir-caprock and its associations, emphasis on anatomizing petroleum-entrapped systerm,properties of natural pools reservoirs and oil-gas accumulation regular pattern of Steep structure gas reservoirs, analysed Permian organic reef type,reef-building sequence,properties of natural pools reservoirs and model for formation reservoir ,and basic properties ,oil-gas accumulation regular pattern of middle Traiassic stratigraph reservoir. Based on above integrational research, forcasted oil-gas exploration prospect in the field investigation, we pointed out that South Daba mountain nappe front zones and Micang mountain foreland basin should be paid more and more attention to.