摘要
井间地震勘探的目的是获得主频和分辨率都很高的地下记录。然而 ,目前的井间地震勘探陷进了一个误区 ,即井间地震勘探的大部分射线都落在临界角以外的区域。本文通过对一些实例的分析 ,确信井间地震勘探的射线入射角小于或大于临界角是成功或失败的标志。文中采用弹性波波动方程正演模型论证 ,当地层水平时 ,在井下激发 ,地震波场在左、右两侧很快超过了临界角 ,形成极为复杂的波场紊乱区 (笔者称之为“牛角尖”)。在这个区域内 ,射线理论已经不再适用 ,初至也无法准确拾取 ,造成了井间成像的极大困难。据此 。
The object of cross hole seismic exploration is to obtain the underground seismic data having both higher frequency and high resolution.But recent cross hole seismic exploration has fallen a pitfall,that is,most of the rays in cross hole seismic exploration is in the region beyond critical angle.Through some cases analysis,the paper determined whether the incident angle of ray in cross hole seismic exploration being less than critical angle or larger than critical angle is the mark of success or failure.Adopting forward modeling of elastic wave equation in the paper,when beds are horizontal and shooting is in the borehole,the seismic wavefield quickly surpasses the critical angle on both left and right sides,formed very complex wavefield confusion zone (the authors call it as 'the tip of a horn').The ray theory is no longer available in this zone.The first break cannot be correctly acquired,resulted in very difficult of cross hole imaging.Therefore,the paper clearly pointed out that the way out for the next developing cross hole seismic exploration lies in controlling the incident angle of ray within critical angle and ensuring the source to have sufficient energy.
出处
《石油地球物理勘探》
EI
CSCD
北大核心
2004年第1期1-11,共11页
Oil Geophysical Prospecting
