虚源法相关道集噪声压制技术

Suppress of virtual source method's correlated gather noise

复杂近地表条件通常制约着常规地震勘探的成像精度,而虚源法可以通过逆时重构消除近地表的影响,实现前提为检波器放置于复杂近地表之下,其优点是在处理阶段不需要建立复杂的近地表速度模型.本文首先通过逆时原理和扰动理论对虚源法的理论基础进行了研究,通过对虚源法的实现方法进行对比,得出结论:上下行波分离与加时窗结合的实现方法可以有效压制有限震源孔径造成的成像假象.验证了利用边缘道衰减压制互相关道集边界效应的有效性.

Complex near surface conditions usually restricts the imaging accuracy of conventional seismic exploration,the virtual source method uses time-reversal logic to eliminate the effects of complex overburden, which requires place geophone under overburden in the acquisition phase,its advantage is that no knowledge of the overburden velocity model is required. Firstly,we carry on the physical interpretation of the virtual source method based on time-reversal technique and perturbation theory. Then,three different implementation ways of the method are compared,conclusion can be drawn： combination of wavefield separation and gating can effectively eliminate the artifacts caused by the limited source aperture typically used in practice. Edge trace attenuation is verified to suppress the edge effect of cross-correlation gather.