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研究发现在番禺—流花地区发育有大量气烟窗现象,气烟窗现象对气田勘探具有重要的意义.天然气沿断层运移扩散造成气烟窗区域地层呈非均质性,影响地震成像,在时间域剖面出现同相轴下拉现象,为改善成像效果恢复地下真实构造,选用叠前深度偏移方法;由于气烟窗内部地震资料信噪比较低,速度建模的精度往往无法满足叠前深度偏移的要求.本文从正演模型出发,结合气烟窗分布范围,以气烟窗区域内外实际井速度差趋势为依据来对速度进行精细调整,在深度域消除了同相轴下拉现象,将该方法应用到实际资料中取得了很好的效果.
The study found that a large number of gas smoke windows were developed in Panyu-Liuhua area, and the phenomenon of gas smoke windows was of great significance to exploration of gas fields. The gas migration and diffusion along the fault caused the heterogeneity of gas smoke windows in the area and affected the seismic imaging. In order to improve the imaging effect and recover the underground real structure, the prestack depth migration method is selected. Because of the low signal-to-noise ratio of the seismic data in the gas smoke window, the accuracy of velocity modeling often can not satisfy the prestack depth Offsetting.From the forward model, this paper adjusts the velocity finely according to the distribution range of the gas smoke window and the actual velocity difference inside and outside the gas smoke window area, and eliminates the pull-down phenomenon in the depth field, This method has been applied to the actual data obtained good results.