复杂近地表多次波分析及压制方法探讨——准噶尔盆地腹部地震资料处理实例

Analysis of complex near-surface multiple waves and discussion on suppression methods:a case of seismic data in the hinterland of the Junggar Basin

准噶尔盆地腹部地区地表主要是沙漠区和公益林区,从东西向剖面分析得知这两种地表对应的波组特征、频率及相位特征差异明显,造成了地震剖面上明显的"阴阳脸"现象。为此,针对不同地表的单炮记录,分析初至频谱存在"陷波"特征的原因;结合表层结构及正演模型论证分析,认为复杂近地表多次波是产生"阴阳脸"现象的主要因素;明确了陷波强弱及产生的具体位置,进而提出基于旅行时差异及自相关第一波谷时间差异的空变预测步长反褶积技术,对该区近地表多次波压制效果明显,改善和消除了"阴阳脸"现象。该方法在准噶尔盆地腹部其他区块中推广应用,均见到良好效果。

The surface in the hinterland of the Junggar Basin is mainly desert and ecological forest.From the analysis of the east-west section,it is known that the wave group characteristics and the frequency and phase characteristics corresponding to the two types of surface are greatly different,which results in the obvious "Yin-yang face" phenomenon on the seismic section.Therefore,considering the single shot records on different types of surface,we analyzed the reasons for the "trapping" characteristics in the first-break frequency spectrum.Combined with the demonstration and analysis of the surface structure and forward model,we believe that complex near-surface multiple waves are the main factor causing the "Yin-yang face" phenomenon.Moreover,the strength and specific location of trapping are clarified,and thus this paper proposes a predictive variant-step deconvolution technology based on the difference of travel time and of the time of the first trough in autocorrelation, which has an obvious suppression effect on near-surface multiple waves in this area and improves and eliminates the phenomenon of "Yin-yang face".This method has been widely used and applied in other blocks in the hinterland of the Junggar Basin,and good results have been achieved.