Syndepositional Fault Analysis And Its Effect On Sedimentary System In Liaozhong Depressing, Bohaiwan Basin

Bohaiwan is a faulted basin, developing in Meso-cenozoic,East China.Liaodong- wan depression is located in north-east of Bohaiwan basin, made up of Liaodong uplift,Liaozhong depression and Liaoxi low uplift. It is an important oil and gas-bearing district of the Shahejie and Dongying formation. Hydrocarbon generation, migration and accumulation are closely related with tectonic activity.With the guidance of Structure Geology, Basin Analysis and Sequence Stratigra- phy, added with seismic and well log interpretation, the structure-stratigraphy framework is established. The central sediment of the basin and development of depsional systems are mainly controlled by syndepositional faults and their activity.There are a lot of faults in Liaozhong depression.Most of them are normal faults with large scale,developed in different time. Main syndepositional faults are recognized and three mainly fault strike are North East, North-North East and East -West.The syndepositional faults are divided into four groups horizontally:“comb-like structure”,“broom-like structure”,“fork-like structure”and“echelon-like structure”; and into five patterns vertically:“fork-like structure”,“pony's tail-like structure”,“feather-like structure”and“Y-like structure”.Three group of syndepositional faults in Liaozhong depression are controlled by different tectonic system.Liaoxi faults are in extensional tectonic system;Liaozhong faults are influenced by both extensional tectonic system and strike-slip structure; Liaodong faults are mostly strike-slip fault. By calculating the Growth Index and activity rate, the active intensity of syndepositional faults is medium to highin and variable. From Paleogene till now, the active intensity of syndepositional faults is easing off. But on the whole, the active intensity in eastern basin is intenser than the western basin.Combined the thickness charts and sedimentary facie, it is obviously that development and activity of synedimentary faults controlled sedimentary sequence development and sandbody distribution. Basin Margin Syndepositional Faults controlled the development of a depression. The Liaodong uplift steep slope break controlled the development of the fan delta system; the Liaoxi slope marginal fault controlled the the growth of the braided delta system; Syndepositional Faults controlled the development of a secondary sag and the development of the Sublacu- strine fan .Guided by hydrocarbon bearing system theory and combined with the relationship between syndepositional faults and reservoir & hydrocarbon resources rock, two favorable places for prospecting are supposed: JZ27 well field in Liaozhong depression,south of Jinxian.