Study on the Sedimentary Microfacies Based on Medium Term Base-level Cycle Change:A Case of the Q4 Member in Fuyu Oilfield,Songliao Basin

Based on the regional sedimentary background and the core and logging data,and from an analysis of its facies markers,such as rock type,granularity distribution,sedimentary structure,mudstone's colors and geochemical features,Q4 Member in Fuyu Oilfield,Songliao Basin is identified as in a deltaic deposition which includes delta plain and delta front.The delta plan is composed of branch channel,crevasse splay,natural levee,abandoned channel,and so on.The delta front is composed of underwater distributary channel,mouth bar,distal bar,underwater nature levee,and so on.The genetic type and the development model of sedimentary facies are closely related to the stratigraphic framework.Under the control of the medium-term base level cycle,the quantitatively identified graphic tablet of microfacies is established,based on the application of coring wells.The sedimentary facies of non-coring wells are quantitatively identified and finely classified under the guidance of the identified graphic tablet.According to the analysis results of the sedimentary microfacies,the planar and sectional distribution maps are obtained.The laws of microfacies distribution on the plane and in the vertical direction are analyzed.In order to reveal the relationship between sedimentary microfacies and the oil,the control effects of sediments on oil are further discussed.It is shown that the channel sand bodies have the best performance in development size,continuity,reservoir quality and oiliness,followed by the mouth bar sand bodies.These results can be used for further oilfield production adjustment and development.