VSP资料的程变反Q滤波

DISTANCE VARYING INVERSE Q FILTERING IN VSP

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。

VSP means Vertical Seismic Pofiling. Because its receivers are located in different depths of a well, it is regarded as the only way to get valuable information about the earth absorption. According to the field survey results of the earth’s attenuation through VSP, it is possible not only to interpret the lithologic characters but also to compensate the loss in energy. At present, many existing methods for inverse Q filtering are focused on dealing with surface seismic data, which we called non distance varying inverse Q filetring, or applied to VSP data processing after wave field splitting. Therefore, VSP is different from the surface seismic data in travel time. In VSP, the direct downward wave is one way and the upward wave is between one way and double way, so the travel time of VSP is not the same as that of the surface seismic data, which results in the different attenuation between VSP and surface seismic data. The algorithm of inverse Q filtering in VSP which we called non distance varying inverse Q filetring is deduced in this paper. It includes a rectifying factor. The results of VSP numerical experiment show that the method is superior to any other existing ones. On the other hand, the experiment also denotes that the compensation for amplitude and the frequency attenuation of VSP record are really improved obviously, which confirm the effectiveness and accuracy of the method presented in this paper