The Study On Sedimentary Microfacies Of The Upper Guantao Formation In The Eastern Liuxi Oilfield Of Raoyang Sag

Guided by high-resolution sequence stratigraphy and sedimentology theory,the geological data such as core,well logging and seismic are comprehensively utilized,and the stratigraphic division and comparison work is carried out through the combination of well and seismic.The Guantao Formation in the study area is divided into three oil layers groups(four-level sequence),seven sand layer groups(five-level sequence),the upper four sand layer groups can be further divided into 16 sub-layers;Under the control of the stratigraphic framework,starting from the core observation,combined with particle size analysis and well logging analysis,the two types of sedimentary facies,such as the meandering river and the braided river,are identified.The braided river includes River subphase and inter-channel subphase;Meandering River includes river subphase,embankment subphase,Floodplain subphase and abandoned river subphase.Each subphase can further divide a variety of sedimentary microfacies.The seismic time windows corresponding to each sub-layer are established.On this basis,multiple seismic attributes of each sub-layer are extracted.Through the correlation analysis of attribute-sandstone thickness,it is concluded that there is a high correlation between root mean square amplitude and average instantaneous phase and sand thickness.However,due to the poor mapping effect of average instantaneous phase attributes,the RMS amplitude attributes are mainly used to predict the distribution of sand bodies in the well-free area.Taking well data as the main basis and seismic attribute map as the reference,the isoline maps of sandstone thickness and plane distribution maps of sedimentary microfacies in each sublayer are drawn,and the plane distribution characteristics of sand bodies and sedimentary microfacies in each sedimentary period are systematically analyzed;The results show that Ng2is dominated by high-curvature meandering river sediments,and the channels are mostly strip-like,with higher curvature but smaller scale.The channel scale of Ng₂¹ sand group is slightly higher than that of Ng₂² sand group;In the Ng₁² sedimentary period,due to the decrease of baseline level and the increase of sediment supply,the scale of the channel increased,and the types of sedimentary facies changed,from meandering river to low-curvature meandering river-braided river;In the Ng₁¹ sedimentary period,the baseline level declined further,the river scale expanded further,and most of them were broadband or flaky distribution,and the heart beach was relatively developed.It belongs to typical braided river deposits.Five quantitative parameters are extracted,including channel width,full bank depth,width-depth ratio,channel curvature and channel sand bar(point bar)scale.The shape and scale of the channel are quantitatively processed.The correlation model between different parameters is established,and the geological database of this area is established,which lays the foundation for quantitative sedimentology research in this area.Based on the above analysis results,combined with the analysis of local structural characteristics and reservoir physical characteristics,seven favorable targets are selected.