Relationship Between Tectonic Evolution And Hydrocarbon Accumulation In Binchang Area Of Southern Ordos Basin

Tight oil is an important part of petroleum exploration and development.It is helpful to study the structural factors of tight oil accumulation,thus favoring the mechanism revealing of potential structural factors.The structure of Binchang Area in the southern Ordos Basin is complex,but the study on the structure mechanism affecting hydrocarbon accumulation is not deep enough.The structural interpretation is conductive to restore the tectonic evolution of Binchang area and establish a suitable reservoir forming model.Therefore,this paper chose the tight sandstone reservoir of Chang 8 oil-bearing formation in Binchang area as the research object,by the aid of three-dimensional(3D)seismic interpretation and and of regional tectonic evolution to analyze the fault characteristics and divide the stages of tectonic activity.By doing this,we can reveal the influence of tectonism on the oil-gas accumulation of this area,establish the model of oil-gas accumulation,and determine the main accumulation periods.The main conclusions were summarized.(1)Along the same fault,the strikes and dip angles are different.The fault appearedon the profile at intervalsand the fault width and break distance were various showing obvious periodicity.In general,the faults have initiated typical ribbon effects horizontally and vertically,suggesting obvious multi-stage and inheritance characteristics.(2)According to the cutting relationships between faults and strata,the periodicity and activity of fault development can be determined.The Mesozoic faults in Binchang area experienced three periods of tectonic activity including the earlier thrust compression fault system in Indosinian,middle torsional strike slip fault system in the mid-late Jurassic,and the fault system from the mid-late Cretaceous to the early Paleogene.(3)The relationship between structure and hydrocarbon was discovered.The fault of Yanchang Formation was mainly developed in late Triassic and mid-late Jurassic,and the timing of structural setting was earlier than the hydrocarbon accumulation,providing migration channel and reservoir space for hydrocarbon migration and accumulation.Then,a series of new faults were formed in the late Early Cretaceous,or reactive the old faults,thus resulting in the adjustment of early hydrocarbon.In the final late Cretaceous Himalayan period,the strata were uplifted slowly,the active faults in this duration provided the migration path for hydrocarbon readjustment.