多次波衰减技术的应用研究

APPLICATION AND RESEARCH ON MULTIPLE REFLECTION ATTENUATION TECHNIQUE

伊犁盆地伊宁凹陷发现有多次波严重影响目的层段反射的现象 ,虽经预测反褶积、波动方程外推以及 f-K等压制多次波 ,但在叠加剖面上收效甚微。文章经分析认为 ,该区目的层段反射系数较小 ,工区构造复杂 ,断层很多 ,加上多次波严重干扰 ,当时野外采集参数无法使有效波与多次波很好分离 ,也就无法使有效波获得足够高的讯噪比。拉冬域滤波是利用动校后的CMP道集在拉冬域的多次波剩余时差 ,根据工区多次波的频带范围 ,要求低频段在最小炮检距处的多次波剩余时差应超过四分之一周期以上 ,而最大炮检距处的多次波剩余时差必须比最小炮检距处超出一个低频视周期以上 ;要求高频段在最大和最小炮检距处的多次波剩余时差差值不能超过 (N - 4 )倍的高频视周期 ,这样就可确保多次波落入叠加方向特性的压制区。文章还结合该区最新采集的地震资料 ,处理中利用拉冬域滤波方法并结合内切除 ,对衰减伊宁地区多次波有明显效果 。

The phenomenon of the interest interval′s being seriously influenced by multiple reflection was found out in Yining Sag of Yili Basin.Through rejecting the multiple reflection by predictive deconvolution ,wave equation extrapolation and f-K relationship,etc.,only very little effect produced on the stacked profile map.Through analyzing in the paper,it is considered that it was unable to make the effective waves be well separated from the multiple reflection by field acquisition parameters,in other words,it was unable to cause the effective waves to get a high enough signal-to-noise ratio because of the interest interval′s small reflection coefficient,complex structural conditions,a large number of faults and multiple reflection′s serious interference in the region.The Radon domain filtering is that,by applying the residual multiple reflection moveout of CMP gather after normal moveout correction in Radon domain and according to the frequency band field in the region,it is required that,in low frequence section,the residual multiple reflection moveout at the minimum offset should be in excess of more than quarter cycle and the residual multiple reflection at the maximum offset must be in excess of above a low frequence apparent cycle as compared with that at the minimum offset;and that,in high frequence section,the difference between the residual multiple reflection moveout at the maximum offset and that at the minimum offset can′t exceed the high frequence apparent cycle by a factor of N minus 3,thus ensuring the multiple reflection′s being fallen in the rejection area of stack direction property.Through processing the newest acquisitive seismic data by use of Radon domain filtering method and in combination with internal mute,it was proved that the effect on attenuating the multiple reflection in Yining Sag is obvious,thus providing effective processing methods and experience for rejecting the multiple reflection in this region in the future.