两种海底多分量波场分离方法的模型测试及改进

The model testing and the improvement strategy for two decomposition methods of seabed multi-component seismic recordings

海上多分量地震勘探能够提供丰富的海底地层信息,有效降低常规纵波勘探的多解性,在气云成像和流体检测等方面具有优势。由于海上多分量资料一般由四分量海底电缆(4C-OBC)采集,可以同时记录上行和下行纵、横波,因此波场分离处理十分关键。首先介绍了SCHALKWIJK和EDME两种常用的波场分离计算公式,然后采用海底水平多层介质模型对其进行了测试,并与在波场延拓时采用亥姆霍兹算子和坡印廷矢量分离得到的上行和下行纵、横波理论记录进行了对比;最后,针对两种常用波场分离计算公式无法剥离上行微屈反射等干扰波的问题,根据海底界面波型转换关系推导得到上行声波有效反射波和PP型纵波的计算公式,可以有效剥离水检上行分量的微屈反射和上行纵波分量的转换纵波。

Many necessary messages about gas reservoir can be obtained from ocean multi-component seismic prospecting, which effectively reduces the multi-solutions of conventional P-wave prospecting and has the advantages of gas-cloud imaging and fluid detecting.As ocean multi-component data is usually recorded by 4C sensors on the ocean bottom cable, abbreviated as 4C-OBC, the down-going P-wave and S-wave will be received as well as up-going P-wave and S-wave.Therefore, wavefield decomposition is the key problem for ocean multi-component seismic exploratioruIn this paper, SCHALKWIJK and EDME the two common calculation formulae of wavefield decomposition are introduced firstly.Secondly,both methods are tested on a ocean seabed horizontal layered medium model, and the decomposition results of their testing recordings are compared with the theory solutions, which are calcu- lated by applying Helmholtz operator and Poynting vector at every wavefield extrapolation.Finally, the two common wavefield de- composition calculation formulae can＇t separate pag-leg reflection of up-going interference wave.The calculation formulae of reflec- tions from up-going PP wave of P-wave is derived based on the waveform, transformation from marine interface not only by sepa- rating peg-leg reflection from up-going hydrophone component, but also by separating S-P wave from up-going P-wave component.