Base-level cycle analysis of wet alluvial fan based on the hydrodynamic energy——By taking well block D of Liaohe oilfield as an example

Based on the theory of high-resolution sequence stratigraphy and by taking Guantao formation of well block D in Liaohe oilfield as an example,this paper studies the relationship between the change of hydrodynamic energy and the response of the base level cycle in the middle period of the wetted alluvial fan.The results show that the change of hydrodynamic energy could reflect the type of the wetted alluvial fan microfacies.When the hydrodynamic energy is not interrupted during the whole base-level cycle,the baselevel cycle could be divided into gentle rising period,rapid decline period,gentle decline period and rapid decline period based on the hydrodynamic energy.A/S value has a great relationship with hydrodynamic energy,and the A/S value could indicate the rising or decline state of the base-level cycle.Based on the difference of the accommodation space,the rapid decline period could be divided into high accommodation space state and low accommodation space state.When the hydrodynamic energy is interrupted at some stage of the whole base-level cycle,no sediment could be preserved.According to the change of the preserved sediment thickness in the middle-term base-level cycle,the change of the long-term base-level cycle could be obtained,and then the long-term base-level cycle could be used to analyze the progressive or regressive state of the wetted alluvial fan complexes and the migration of the high accommodation space along the source direction.