基于气烟窗模型正演恢复真构造实验分析

Experimental analysis of gas chimneys structure reconstruction based on seismic model

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.

Gas chimney are found in abundance in panyu-liuhua field. Gas chimneys make significant contribution to gas productivity. The disturbed seismic imaging performance on the time section is the pull-down event,which is caused by gas leaking. In this paper,pre-stack depth migration（ PSDM） is chosen as a means to improve imaging quality and get the true information of subsurface structure. Actually,because of low signal to noise ratio of seismic data in this area,the precision of velocity cannot reach the standard of PSDM. Based on seismic modeling,we adjustment the velocity field according to the spatial distribution of gas chimneys and the trend of the statistics velocity difference inside and outside the gas chimney form well logging curves. This method is put into practical use with good effect,it can improve the pull-down event to a large extent.