Multi-stage structural deformation features and hydrocarbon accumulation in faulted basin: a case study in Nanbeier Sag of Hailar-Tamtsag Basin

The control of structural style on petroleum was analyzed through studying the relationship between multi-stage tectonic deformation features and the main factors controlling hydrocarbon accumulation,such as sedimentary filling type,hydrocarbon source rock generation feature,trap type and pathway system,etc.The controlling effect of structural style on petroleum in basin and depression was analyzed.From the aspect of basin level,structural deformations from non-rotating graben/rotating half graben,rolling half graben,duplex half graben,to slip half graben generated in the Nanbeier Sag during tectonic evolution.Various sag structures determined the filling types of sedimentary system and the distribution features of sand body,further influenced the generation and distribution of source rock,resulted in various hydrocarbon generation and accumulation assemblages in different formations,and finally controlled the superimposed composition of various reservoir types.Tectonic styles were classified into 3 stages,3 big types(rift type during chasmic stage,extensional-twist type during fault and depression stage,and torsional reversed type during inversion stage) and 18 types.Compressional structures of inversion stage were advantage points in secondary oil reservoirs.The structural styles of faulted-depression and inversion stage constructed multiple types of fault-sand body pathway system.The deformation features of fault basin controlled the key elements for hydrocarbon generation,reserve,trap and migration,and further determined the distribution of oil and gas.