Deepwater sedimentary association of Chang 6 oil bearing formation|
Yanchang Formation of Huaqing Oilfield in Ordos Basin
Deng Xiuqin1,2,3 Li Wenhou1 Li Shixiang 2,3 Du Yuguo2,3
1.Key Laboratory for Continental Dynamics of the Ministry of Education, Department of Geology,Northwest University|Xian 710069； |2.Exploration and Development Research Institution of Changqing Oilfield Company|Xian 710018； |3.National Engineering Laboratory for Exploration and Development of LowPermeability Oil &|Gas Fields|Xian 710018
Located in the depositional central of Ordos Basin in Late Triassic，the sedimentary of Chang 6 oil bearing formation in Huaqing area is characterized by mixed sources and deepwater deposition association which can be divided into three types，ie semideep lake and deep lake sediment，gravity current sediment and deepwater delta sediment. In different areas and stages，flow state will develop and transform one another. Delta sediment is featured by plentiful crossbeddings. Slump is marked by slide plan，with sudden lithologic contact relationship with overlying and underlying strata at top and bottom generally. Debrite in the study area is featured by development of different sized mud debris and turbidite presents normal grading. In the context of early lake regression，thick sandbody well developed in the central of Ordos Basin. Deposition controlled by northeast provenance is constitute of slump and progradation sand body of delta with thin layers of turbidite，and the deposition，controlled by southwest and west provenances，is constitute of turbidite，debrite and slump. In the mixedprovenance area，sediment is made up of debrite，turbidite and slump.