利用三维多项式曲面拟合的子体波形主成分分析剥离火成岩强屏蔽

火成岩对地震波具有极强的屏蔽和吸收作用，并常形成强反射，造成火成岩下伏地层的地震资料品质变差。为了剥离火成岩强反射，可根据解释的火成岩层位信息设置相应的时窗宽度，通过搜索纵、横向地震波形特征准确获得火成岩层位，实现局部层拉平，再利用子体波形主成分分析(PCA)剥离火成岩强反射。基于此，采用三维多项式曲面拟合代替Wheeler变换实现局部层拉平，形成了基于三维多项式曲面拟合的子体波形PCA火成岩强屏蔽剥离技术，避开了Wheeler变换在实际应用中由于火成岩反射同相轴无法拉平而带来的重构地震信号局部失真问题。同时，在剥离过程中无需引入振幅阈值控制，对于火成岩反射振幅横向变化快的问题，只要在设置的子体窗口范围内火成岩反射振幅变化不大，就可以提取该子体窗口的火成岩强反射，并通过滑动子体窗口，在横向剥离火成岩强反射，提高了方法的实用性。模型测试和实际资料应用表明，该方法剥离的火成岩强屏蔽横向连续性强，能够较准确地剔除火成岩强反射界面的综合响应，在一定程度上削弱了火成岩对下伏地层反射波的屏蔽作用，提高了对地震弱反射的识别能力，为弱信号的能量补偿和后续处理奠定了基础。

Stripping technology of sub-volume waveform PCA based on three-dimensional polynomial surface fitting for strong igneous rock shielding

Igneous rocks have significant shielding and absorbing effects on seismic waves and often generate strong reflections,resulting in poor quality of seismic data on the underlying strata below igneous rocks. For the stripping of the strong reflections from igneous rocks,the corresponding time window width can be set according to the interpreted igneous rock horizon information,and the igneous rock horizon can be accurately obtained by searching longitudinal and lateral seismic waveform features to achieve local horizon flattening. Then,the strong reflections from igneous rocks can be stripped by the principal component analysis (PCA) of the sub-volume waveform. On this basis,three-dimensional polynomial surface fitting,instead of Wheeler transform,is performed to achieve local horizon flattening,and a stripping technology of sub-volume waveform PCA based on three-dimensional polynomial surface fitting is developed for strong igneous rock shielding. This method not only avoids the problems of local distortion of the reconstructed seismic signal caused by the failure of the reflection event of igneous rocks to be flattened when using Wheeler transform, but also saves the need to introduce amplitude threshold control into the stripping process. As for the rapid lateral change in the amplitude of the reflection from igneous rocks,the strong reflection from igneous rocks in the sub-volume window can be extracted and stripped laterally by sliding the sub-volume window as long as the amplitude of the reflection from igneous rocks within this window set does not change significantly,which improves the practicability of the method. The model test and application of practical data show that the proposed method allows for high lateral continuity of the strong igneous rock shielding stripped and that it can accurately eliminate the comprehensive response on the interface of the strong reflection from igneous rocks. In this way,it weakens the shielding effect of igneous rocks on the reflected waves from the underlying strata,promotes the ability to identify weak seismic reflections,and ultimately lays a foundation for energy compensation for weak signals and the subsequent processing of those signals.