强衰减地层VSP反Q滤波方法

本文根据零井源距VSP下行初至波最大振幅随时间的变化趋势，将地层划分为强衰减地层和弱衰减地层。其中地震波衰减最强烈的强衰减地层可认为是由多个层状常Q介质构成，Q值主要利用VSP资料提取；而弱衰减地层认为是Q值大于200、地震波发生的衰减相对较弱甚至可以忽略的地层。在波场延拓反Q滤波方法基础上本文提出VSP强衰减地层反Q滤波，该法弥补了因中、深层Q值难以求准、补偿约束难度较大等因素导致的反Q滤波精度降低的缺陷，使反Q滤波结果更稳定、高效，也为地面地震反Q滤波方法的完善及应用提供有意义的启示。

VSP inverse Q filtering in strong attenuation formations

VSP is used to study seismic absorption and attenuation because of seismic wave acquired in wells. We consider that there are two kinds of formation: strong attenuation formations and weak attenuation formations according to the maximum amplitude variation of down primary wave with time in zero-offset VSP. The strongest attenuation formation is composed by multi constant Q layers, and the Q value in each layer can be extracted from VSP data. While the Q is infinite in weak attenuation formations, and seismic wave attenuation can be ignored. Based on the wave-extrapolation inverse Q filtering, the inverse Q filtering in strong attenuation formations is presented in this paper. Pilot tests show that this proposed approach is more stable and efficient than conventional inverse Q filtering which lead low accuracy due to difficulties in accurate Q value calculation. At the same time, this approach may provide meaningful insights for surface seismic inverse Q filtering.