论文部分内容阅读
因为ＶＳＰ（垂直地震剖面）可在井下不同深度直接观测震源子波的变化，因此被认为是能够提供唯一有价值的地震波衰减资源的来源。利用实际地层中波的衰减测量结果，可以对ＶＳＰ记录的地震波能量损失进行补偿。目前大多数ＶＳＰ的反Ｑ滤波都是直接套用地面地震资料的反Ｑ滤波方法，我们称之为ＶＳＰ资料的非程变反Ｑ滤波法。即对ＶＳＰ经过波场分离和静态时移后得到的上行波分别进行反Ｑ滤波。但是，ＶＳＰ并不像地面反射地震记录那样射线是双程路径的，它的下行直达波是单程走时，而上行反射波的走时介于单程和双程走时之间，因此，ＶＳＰ所记录的地震波衰减程度与地面地震资料所记录的地震波的衰减程度是不同的。本文根据ＶＳＰ上、下行波各自的波场特点，推导出ＶＳＰ特有的反Ｑ滤波数学表达式。该表达式与地面地震记录反Ｑ滤波的表达式所不同的是增加了一个校正因子，该校正因子是传播路程（或传播时间）和品质因子Ｑ的函数，我们称该方法为ＶＳＰ的程变反Ｑ滤波法。经过数值模拟计算表明，该方法对ＶＳＰ的地震波振幅和频率衰减的补偿具有明显的效果。
Because the VSP (Vertical Seismic Profile) can directly observe changes in source wavelet at different depths downhole, it is considered to be the only source that can provide the only valuable seismic attenuation resource. The loss of seismic energy recorded by the VSP can be compensated for using attenuation measurements of the mid-wave of the actual formation. At present, most VSP anti-Q filters are anti-Q filtering methods that directly apply ground seismic data, and we call it the non-varying inverse Q filtering method of VSP data. That is, VSP performs inverse Q filtering on the up-going waves obtained after the wave field separation and the static time-shift respectively. However, the VSP is not a two-way path as the ground-reflection seismogram records. Its downstream direct wave is one-way travel time, whereas the upstream reflected wave travels between one-way and two-way travel times. Therefore, the VSP recorded seismic waves The degree of attenuation is different from the attenuation of seismic waves recorded by surface seismic data. In this paper, based on the characteristics of the wave fields of the VSP and the descending wave, we derive the VSP-specific mathematical expression of inverse Q filtering. The difference between this expression and the inverse Q filter of terrestrial seismograms is the addition of a correction factor that is a function of the propagation distance (or propagation time) and the quality factor Q. We call this method the VSP’s process change Anti-Q filter method. Numerical simulation results show that this method has obvious effect on the compensation of VSP amplitude and frequency attenuation.