Study On Sedimentary Microfacies Characteristics And Reservoir Control Of Gaotaizi Oil Formation In Qijia Area,Songliao Basin

On the basis of understanding the regional geological structure characteristics and stratigraphic sedimentary characteristics of the study area,using the principle of high resolution sequence stratigraphy,the high resolution sequence stratigraphic framework of the high Ⅳ oil formation in Gaotaizi oil layer in Qijia area was gradually established,and the high Ⅳ oil formation was divided into three sets of sand groups,upper,middle and lower,and finely divided into 18 small layers.According to the combination of lithofacies,logging facies and seismic analysis,the main sedimentary facies of Gaotaizi oil formation in Qijia area is delta front facies zone,which can be further divided into underwater distributary channel,mouth bar,sheet sand,interdistributary bay,overflow sand and other sedimentary microfacies.Using seismic sedimentology method,seismic multi-attribute fusion is carried out to analyze the distribution range of sand body,and then analyze the evolution characteristics of sand body.A large number of strata slices of 18 small layers in the high Ⅳ oil formation were made by means of seismic sedimentology.The fast scanning method of strata slices was applied to trace the channel sand body.The sedimentary microfacies maps of 18 small layers in the high Ⅳ oil formation were further described by the combination of well and seismic method,and the sedimentary model of large gentle slope shallow water delta in Qijia area was analyzed and determined.Taking the distribution range of 18 small layers of different types of sedimentary microfacies sandbodies in high Ⅳ oil formation as the target,based on the classification of oil source faults and combining with the structural characteristics of the study zone,the reservoir types and main controlling factors of accumulation are analyzed.It is found that the study area is mainly composed of fault lithologic reservoirs,sand body updip pinch-out lithologic reservoirs and lithologic lens reservoirs.Secondly,anticlinal structural lithologic reservoirs and nasal structural lithologic reservoirs are also developed.The favorable zones are determined based on various control factors,and the optimal selection of favorable zones is finally carried out.The favorable zones in the north of the ring concave gentle slope area are judged to be the best oil and gas enrichment zone with superior structural conditions and well-developed channel sand bodies,followed by the favorable zones in the eastern uplift area with better structural conditions and source rock conditions,and a large number of beach bar sand bodies are developed in the west favorable zone of the ring concave gentle slope area.It can effectively store oil and gas.However,there are relatively few channel sand bodies in the favorable area of the western uplift,and the structural conditions are worse.However,the channel sand bodies are relatively thick and broad,which has a certain reservoir potential.