井炮地震数据的沙漠鸣震噪声特征分析与压制方法

Propagation characteristics and suppression methods of sand duneringing noises in common-receiver gathers

在沙丘连绵起伏的沙漠区,井炮激发的地震波容易产生沙漠鸣震噪声。鸣震噪声在炮集上表现为能量随沙丘高度的变化而变化且没有明显线性干扰波的特征。在三维叠加剖面上,沙漠鸣震噪声沿接收线方向弱,而垂直于接收线方向强。由于鸣震噪声在炮集和主测线上表现不明显,因此在处理过程中容易被忽视。利用层析静校正计算的近地表速度模型进行波动方程数值模拟,在正演记录上可以看到与野外采集数据特征一致的沙漠鸣震噪声。将正演记录和野外数据分选到共检波点道集后,鸣震噪声的线性特征非常明显。在正演模拟记录的波前面上,可以看到与沙丘对应的鸣震噪声。观察波场快照可以看到,沙漠鸣震噪声是折射波能量在地表和潜水面之间多次震荡形成的。由于鸣震震荡周期等于地震波在沙层中的旅行时,所以在共检波点道集上,不同地震道的鸣震噪声具有相同的震荡周期,鸣震噪声表现为线性特征。在地震数据处理过程中,将地震记录分选到共检波点,采用共检波点道集的线性干扰压制方法,可以有效压制井炮数据的沙漠鸣震噪声。

In a desert area with rolling sand dunes,dynamite-excited ringing tends to occur as non-linear noises in common-shot gathers with the amplitude varying with dune height.On 3D stacked sections,ringing noises are weak in the direction parallel to receiver lines and strong in the direction perpendicular to receiver lines.Thus,ringing noises may be neglected in seismic data processing because of their indistinct responses in shot gathers and in inline direction.We use the near-surface velocity model derived from tomographic static correction for numerical simulation based on the wave equation and obtain synthetic ringing noises,which are consistent with field records and show as linear noises in common-receiver gathers.Ringing noises,which correspond to sand dunes at the wavefront on synthetic wave field snapshots,are oscillatory refracted waves between land surface and the phreatic water table.Ringing cycle is equal to the travel time of seismic waves in the sand layer;this means that ringing noises are linear in common-receiver gathers and thus could be easily suppressed after sorting common-shot gathers into common-receiver gathers.