Research On Sedimentary Facies Of Triassic's First Oil Group In Sangtamu Oil Field

The Sangtamu Oilfield is a large-scale compound oil and gas field on the draping anticline belt of the Sangtamu buried hill in the Lunnan slope of the Tabei Uplift.It is an anticline structural belt with a length of about 24 km and about 1 to 2km wide,and the whole is gradually reduced from east to west.The oil and gas resources are abundant,and the Triassic clastic rock is an important oil-bearing series in the oil field.TIII oil group is the reservoir with the largest thickness and the best oiliness in the three oil groups,which a lot of previous studies have been made.While the TI oil group,which has been developed as the replacement layer of the Triassic,is of great significance and is of great significance for exploration and research.The reservoir distribution is controlled by the tectonic factors and sedimentary facies.In this paper,the upper sand body of Triassic TI oil group in Sangtamu oil field is studied in detail from the aspects of stratigraphic division and correlation,sedimentary facies identification,seismic attribute analysis,provenance analysis,facies classification and sand body distribution feature.Based on the core observation,logging curve identification and seismic profile analysis in the work area,the upper sand body of TI oil group is divided into three oil bearing formations(TI1,TI2,TI3)and eight single sand layers by using the method of equal elevation,river cutting and sedimentation control.Combined with trap growth characteristics,an undeveloped independent fault block is preferred as an advantageous zone for the next development.The grain size of the TI oil group is fine,which is mainly fine sand,silt and argillaceous siltstone,and it is also developed.Vertical granularity is normal grading.Sedimentary tectonic is plenty,and the bottom of the cycle is generally the erosion surface as the boundary.Above the boundary,there are festoon cross-bedding,massive bedding,tabular cross bedding,concordant bedding,current bedding and flat bedding.The mudstone contains plant fossils.Logging curves are box-shaped,composite boxshaped,bell-shaped,funnel-shaped,straight section and other forms.The sand body of TI oil group is widely developed,with a thickness of 30-50 meters,gradually thickening from west to east and "sand pack mud" features is obvious.The characteristics of sandbody plane distribution show that the high value area of the sand body is lenticular,and the distribution of the slice is spread in the east and west.The TI oil formation is developed by the braided river delta front subfacies.Part of Sangtamu Oilfield is gradually descending shore shallow lake and most of the work area develops subaqueous distributary channel,far granulated substance dam,subaqueous interdistributary channel,sand sheet and muddy beach microfacies.Based on the study of sedimentary facies and the characteristics of tectonic distribution,it is found that there is an independent undeveloped fault block in the sixth and seventh part of the area in the west of the Sangtamu area,and the oil source condition is sufficient.Sand body inversion results show sand is abundant.Tectonic analysis are considered to have the conditions of forming traps,it is considered that there are oil and gas filling in the traps,so,the Triassic TI oil group in this area can be used as the target area for the next development step.