A Study On Cretaceous Hydrocarbon Accumulation Conditions In Babei Sag, Yin-E Basin

Babei sag belongs to a secondary tectonic unit in the Suhongtu Depression of the Yingen-Ejinaqi Basin.Based on the exploration of Yingen-Ejinaqi Basin,this paper combines the methods of geology-logging-dynamic analysis and the reservoir as the core to clarify the characteristics of the structure,reservoir characteristics,reservoir prediction,oil-water layer division and its vertical Distribution,identification and calibration of the boundaries of reservoirs,intervals and mezzanines,and to clarify the geologic conditions of reservoir-cap assemblage and hydrocarbon accumulation in this area.Mainly made the following understanding:The tracing interpretation of four seismic reflection interfaces of 15 earthquakes in the Babei Sag was completed.The stratigraphic features of the typical rifted basins are shown on the whole.The distribution of sedimentary centers along the distribution of main faults is north-north east or north In the eastward spreading,the thickness of major and minor depressions in the east is large,and the thickness of the minor depressions in the west is thin.The formation strands are thinner toward the south and eastward from the sedimentary center.The Lower Cretaceous Bayingebi Formation has a sedimentary center with a thickness of 160-1000 m.The Suhongtu Formation also has a sedimentary center with a thickness of 150-730 m.The Yingen Formation has three sedimentary centers with a thickness of 30 ~ 850 m.The Early Cretaceous Babei sag entered the period of full development of fault basin,in which Bayingeobi was early stage of fault,Bayinogu period to Suhong period was fault depression stage,and silver root stage was fault depression stage.Bayinogou period ~ Suhong period,Babei sag is a typical faulted basin,and three two ?-level controlled depressions are north-east and north-north east.The ?-level fault and the IV-level fault are well developed and large in scale,making the depression structure complex and the strike of the fault is basically skewed or consistent with the controlled-fault fault.Northeast depression was northwest low,high southeast.During the silver root period,Babei sag basically inherited the structural pattern of the Suhongtu Formation and further transformed into the depression.Since the Bayingebi Formation,due to the tectonic movement,the sedimentary environment has changed into continental facies,with lacustrine facies,nearshore subaqueous fan facies and braided river delta.Dark mudstone and gray mudstone are mainly distributed in Cretaceous Yingen Formation,Suhongtu Formation,Bayingebi Formation and source rock with a thickness of 953.4 m.Organic matter abundance evaluation The above mentioned formations are all poor source rocks except that the second member of the Bayinogobi Formation is a poor ~ source rock.The Yingen Formation and the Suhongtu Formation entered the condensate and moisture phases,and the Bayinogobi Formation entered the oil production window-a large amount of oil-producing period and is the most important source rock in this area.By analyzing and evaluating the source and reservoir caprock,the Mesozoic Suhongtu Formation and Bayingebi Formation Passage 2 are either authigenic or subsogeneic combination.Based on the study of oil source conditions,reservoir conditions,caprock conditions,trapping conditions and supporting conditions,combined with the information of oil and gas displays,taking into account the sedimentary facies belts and structural features,a favorable zone of Bayingebi Formation 1,two favorable zone 4;Su Hong map group two favorable zone 7.