Geological genesis of strong amplitude of sedimentary anticlines and identification of sedimentary facies and reservoirs of Pinghu Formation in Xihu Depression

To find out the relationship between amplitude and lithology of Pinghu Formation in Xihu Depression, this paper analyzes the amplitude changes of coal seam and sandstone when they are thickened or thinned by means of seismic forward modeling and log constrained inversion. The relationships are analyzed between horizon amplitude, inversion speed and lithologic content of different wells. The results show that both coal seam and sandstone thickening can lead to amplitude enhancement, and thin layer interference and fault zones can also cause change in amplitude. The increase of amplitude in the core of contemporaneous anticline is caused by the thickening of sandstone in delta front of lower Pinghu Formation and the increase of coal seam content in delta plain of mid to upper Pinghu Formation. The plane extension and morphology of strong amplitude and the high velocity part of the lower Pinghu Formation indicate the type of river-dependent delta reworked by waves. This conclusion is helpful to the sedimentary facies depiction, reservoir characterization and target evaluation in the region.