Structure Interpretation And Reservoir Prediction Of The 2nd Section Of Nantun Formation Of X Block In Beier Oil Field

X block of Beier oil field is located in the middle and south of Beizhong sub-depression of Beier Depression of Hailaer Basin.The 2nd section of Nantun Formation is given priority to with fan-delta front depositional system in the area.The reservoir is characterized by “thin sand body longitudinally and poor lateral continuity”.Under the influence of many tectonic movements in Hailaer Basin,the characteristics of the 2nd section of Beizhong subdepression are fracture development and complex structure.Based on the theory of high-resolution sequence stratigraphy,the lithological and electrical characteristics of logging curves and the sedimentary cycle characteristics were used to carry out well-seismic combined stratigraphic correlation in the 2nd section of Nantun Formation.The 2nd section of Nantun Formation is divided into three level 4 sequence in this paper.Then,applying the synthetic seismogram calibration,set up four longitudinal transverse isochronous stratigraphic framework.Multi-seismic attribute fusion,full 3D seismic interpretation,integrated well-to-seismic fault identification and other techniques were used to interpret the fault and horizon.Using the constraint of interpretation horizon,the three-dimensional velocity model is constructed to perform time-depth conversion.Finally,the T0 and structural map of the four reflectors in the 2nd section of Nantun Formation were completed.The faults were classified by fault development times,then the characteristics of traps and faults of the 2nd section of Nantun Formation were summarized by combining the plane distribution of faults.Reservoir prediction is studied in two aspects.(1)In the aspect of reservoir qualitative prediction,seismic frequency division attribute analysis technology is used to optimize the seismic attribute suitable for this study area to qualitatively analyze the distribution characteristics of reservoirs.(2)In the aspect of reservoir quantitative prediction,by means of logging curve standardization and normalization,the logging curve is pretreated,and then the sensitive curve which can reflect the characteristics of sand and mudstone in the study area is selected.Finally,the P-wave impedance curve is used for geostatistical inversion.In this study,basic data such as lithology,sedimentary structure and bedding are obtained by observing the cores of 12 wells.On this basis,sedimentary microfacies of core can be identified.Comprehensive analysis of the sedimentary background of the study area,the logging curves are used to identify the single well sedimentary facie.Then,these basic data,including seismic attribute,sandstone percent and thickness,are used to characterize sedimentary microfacies map.The results show that there mainly are fan-delta front subfacies in the 2nd section of Nantun Formation.The main sedimentary microfacies comprise distributary channel,mouth bar,frontier sheet sand.There are three types of oil and gas reservoirs in Beizhong sub-depression,including complex fault block,fault-lithology trap and lithologic trap.The main controlling factor of petroleum entrapment is source rock,fault and reservoir in Beizhong sub-depression.The tectonic zone is a favorable area for oil gas migration and accumulation.The higher part of local structure is generally better oiliness and high yield.Based on the fine structure interpretation,the study predicted the favorable zone in the 2nd section of Nantun Formation by analyzing the structural characteristics,fault properties,reservoir distribution,sedimentary facies distribution and accumulation characteristics.