OBN资料三维水层相关多次波压制方法研究

3D water-layer-related multiples attenuation for OBN data

海底节点(OBN)采集技术具有灵活、高效、宽频和宽方位等优势,但后续地震资料处理面临诸多难题,其中,水检P分量和陆检Z分量经双检合并后所得上、下行波中水层相关多次波压制就是亟待解决的难题之一。为此,根据OBN炮点密集、检波点稀疏以及在海底较平缓情况下水层相关多次波在平面波域近似呈周期性分布的特点,利用平面波域波场延拓的方式实现共检波点道集上、下行波水层相关多次波预测。该方法首先将OBN共检波点道集资料利用双检合并技术进行上、下行波分离;然后根据检波点处水深信息在平面波域进行波场延拓预测水层相关多次波;最后利用自适应匹配相减技术实现水层相关多次波压制。三维理论模型和实际资料测试结果表明,该方法能有效预测水层相关多次波,实现OBN资料真三维水层相关多次波的压制。

Ocean bottom node(OBN)acquisition is preferred by the industry because of its flexibility,high efficiency,broad band,and wide azimuth.However,seismic processing of OBN data is challenging and,in particular,the water-layer-related multiples attenuation is difficult.The OBN acquisition is characterized with dense shot points and sparse receiver points.The water-layer-related multiple is approximately periodic in the plane wave domain for relatively flat seabed.In this study,wavefield continuation in the plane wave domain was proposed to predict this kind of multiple for the common receiver gathers.First,the upward and downward waves were separated using the dual-sensor merging technique,as the polarities of the P-and Vz-components are concordant for the upward waves while the opposite is true for the downward ones.Then,the so-separated waves were transformed into plane waves.Next,wavefield continuation in the plane wave domain was conducted with the receiver depth information to predict the water-layer-related multiple.Finally,the predicted multiple in the plane wave domain was transformed back into the time-space domain,which was adaptively subtracted from the input gathers.The proposed method was achieved in 3D,which is a requirement in case of wide-or full-azimuth acquisitions.Tests on a 3D theoretical model as well as on field data showed that this method can effectively predict and attenuate the water-layer-related multiples.