基于克希霍夫衍射理论的水层多次波预测方法

Water-layer multiple prediction method based on Kirchhoff diffraction theory

在海洋地震勘探中,水层多次波是一种常见的干扰波.水层多次波的存在常常会造成地震资料分辨率降低,损伤地震资料频带,产生虚假同相轴等假象,严重影响波组特征与地震资料解释.SRME(Surface Related Multiple Elimination)和MWD(Model-based Water-layer Demultiple)方法的提出为多次波预测压制提供了有效的解决方案.但SRME方法并不能适用于浅水以及起伏海底的OBC(Ocean Bottom Cable)观测数据的多次波压制,而常规的MWD方法构建格林函数进行多次波预测时仅仅考虑了地震波在传播过程中产生的时移和几何扩散等运动学特征,不能很好地将多次波进行精确的重建.为了解决上述问题,本文基于克希霍夫衍射理论在格林函数中加入角度算子,使预测结果更加准确、更具有动力学特征,并根据多次波射线路径提出了一种相对更加灵活的适用于浅水的水层多次波预测方法,精确预测了水层多次波,结合曲波域多次波提取技术使水层多次波得到了有效压制.

Water-layer multiple wave is a kind of common interference in offshore exploration. The presence of water-layer multiple often causes poor quality of resolution, damage of frequency band and false event and seriously impacts wave characteristics and seismic interpretation. Proposed SRME （Surface Related Muhiple Elimination） and MWD （Model-based Water-layer Demuhiple） method provides an effective solution for multiple prediction and attenuation. But SRME method does not suitable for shallow water and OBC （Ocean Bottom Cable） multiple suppression in rugged seabed. While the conventional MWD Green＇ s function method for multiple prediction only considering the kinematic characteristics as time shifting and seismic waves geometric spreading, accurate reconstruction of multiple cannot be achieved. Based on Kirchhoff diffraction theory, angle operator is added in the Green＇ s function and make the prediction more accurate and more dynamic characteristics. And in order to solve the above problems, this paper presents a relatively more flexible water-layer multiple prediction method which is applicable to shallow water, based on multiples of the ray path. Accurate water-layer multiple was predicted with this method, and combining curvelet domain multiple extraction water-layer multiple is effectively suppressed.