High Resolution Sequence Stratigraphy And Sedimentary Microfacies Research Of Quantou Formation In Fulongquan Fault Depression, Songliao Basin

The Fulongquan fault depression,located in the southern part of Songliao Basin,which experienced a number of tectonic evolution processes.The aim of this paper is to establish a high-resolution sequence stratigraphic framework by studying the Quantou Formation in Fulongquan area,Songliao Basin.On this basis,the distribution characteristics of the sedimentary microfacies of the Quantou Formation are defined,and the distributing range of the favorable reservoir in the Quantou Formation is determined,which provides a geological basis for the exploration and development work of Quantou Formation.In this paper,high-resolution sequence stratigraphy was divided for the Quantou Formation in the Fulongquan fault depression,and the Quantou formation was divided into four third-order sequences(Quan 1st,2nd,3rd,and 4th,only Quan 1st to 3rd are studied)and eight quartic sequences.In this paper,only one to three stages of the spring and eight quartic sequences are studied.The characteristics of the third-order and fourth-order sequence interfaces and the structural types of each sequence are analyzed.Finally,the high-resolution sequence stratigraphic framework of the Quantou Formation in the Fulongquan fault depression is established.The type of the Quantou Formation and the microfacies were identified.The transition from braided river to meandering river happened from the lower section to the upper section of Quan 1st.Quan 2nd and 3rd fully developed meandering river sediments,and mainly sedimentary microfacies are river channels,abandoned river channels,crevasse fans and flood plains.Within the high-resolution sequence stratigraphic framework,the distribution characteristics of oil and gasbearing sand bodies of Quantou Formation were analyzed.The channel sands of the fluvial facies in the Quantou Formation are the main types of favorable reservoir sandstones,with mainly Type I and Type II reservoirs.The oil-bearing reservoir sand bodies are mainly distributed in the lower section of Quan1 st,the lower and middle sections of Quan 2nd and the lower of Quan 3rd.The thickness of sand bodies in other parts of Quantou Formation is thin,physical properties are fine,so oil and gas show less.In the plane,the favorable reservoir facies belts of the lower section of Quan 1st to the upper section of Quan 2nd,are mainly concentrated in the central area of Yongan,Funan,and Fubei,and only small part of the Gujiadian area.The favorable reservoir facies belts of Quan 3rd are mainly concentrated in the central area of Yongan and Funan.