Research On Sequence Stratigraphy And Sedimentary Facies Of Nan Tun Formation In Wunan Sub-depression

With complex geological conditions, Wuerxun Sag is one of the most potential exploration areas in the Hailaer Basin. To meet the need of exploration development trend, it is necessary to further research sedimentary facies and accumulation conditions in sequence stratigraphy framework.Based on the characteristics of terrestrial depositional basin and the identification marks of sequence boundaries according to the theory of sequence stratigraphy, Nan Tun formation of Wunan sub-depression is divided into 2 third-order sequences and 8 fourth-order sequences. By sequence stratigraphic division and correlation for the main wells and seismic profiles, the corresponding sequence stratigraphy framework was established.In the sequence stratigraphy framework, synthesizing the materials of sedimentary microfacies, across-well facies and seismic attributes, we discover fan delta-lake depositional system, lacustrine depositional system and sublacustrine fan deposition system are mainly developed in Nan Tun formation of Wunan sub-depression. What's more, fan delta front subfacies are the most favorable reservoir blocks and have the closest relation to oil and gas exploration.On the basis of sequence division, the research of sedimentary facies and previous research achievements, three favorable zones have been optimized in the member Klnl of Wunan sub-depression, where slope break belt is the most favorable exploration area. In the member Kln2 of Wunan sub-depression, three favorable zones have been optimized and southern part is the most favorable exploration area.