克希霍夫法VSP多波联合成像

VSP multiwave image with Kirchhoff Method

VSP转换波跟VSP纵波或常规地面转换波相比,具有较高的分辨率和信噪比,但传统的VSP成像方法只利用了反射P波信息,而把转换波(反射S波、透射S波)以及透射P波当作影响成像质量的噪音.本文给出了一种VSP共炮点道集多分量地震资料克希霍夫法偏移成像的方法.本方法充分利用了多波(反射P波、反射S波、透射P波、透射S波)信息,根据转换点处四种波同时起跳,能量叠加最大的原理,从接收点分别用向绕射点延拓它们的能量,并将其叠加起来,求得的和最大的一点即反射点.通过模型试算和实际资料处理表明,此法成像精度高,信噪比高,且有利于改善剖面的频率特性.

VSP converted PS waves have higher resolution and S/N ratio than both VSP P wave and converted waves in surface seism, but almost all of the known method of VSP image use only reflected P wave, and treat the converted waves （reflected P-S wave and transmited P-S wave） and transmited P-P wave as noise resulting in poorer migrated images. This article shows a Kirchhoff image method for common-source point gather of multi-component VSP data. This method sufficiently makes use of multiwave（reflected P-P and P-S wave, transmited P-P and P-S wave） information. On the basis of the principle that the stack of the energy of the four waves should be the largest at the reflection point, when we make the backward continuation of the four waves＇ energy from the geophones toward the image point, and add them together, the point that the sum of the energy is the largest is the reflecting point. Modeling and field data imaging results show that the method is accurate and can improve the S/N ratio and frequency character of seismic section.