弹性波联合叠前逆时偏移数值试验

Numerical experiments on the elastic wave united prestack reverse-time migration

与常规纵波地震资料相比,多波多分量地震资料含有更为丰富的弹性波场信息,因此,研究多波多分量弹性波场的逆时成像方法可以更好地挖掘其潜在的应用价值。从非均匀各向异性介质弹性波波动方程出发,尝试从弹性波正演过程来计算纵波/准纵波初至走时,并以此走时作为弹性波联合叠前逆时成像值的筛选条件;同时给出了具体的逆时成像原理和计算步骤,并引入基于散度和旋度的纯纵、横波的波场分离算子,最终实现了弹性波波场中混合波场、纯纵波和纯横波(转换波)波场的联合逆时成像。均匀弹性介质模型算例验证了所提出的走时计算方法的准确性和有效性;各向异性弹性介质模型的数值模拟试验结果表明,所给出的弹性波联合叠前逆时成像方法能够考虑介质岩性和构造特征的复杂变化,获得符合理论和实际地质情况的成像结果。

Compared with conventional P-wave seismic data,multi-wave multi-component seismic data contains more elastic wavefield information.Therefore,the potential application value could be discovered by the research on the imaging method.Starting from the elastic wave equation of heterogeneous anisotropic medium,experiments on the computation of the P-wave/quasi-P-wave’s first-arrival traveltime are carried out at the elastic wave simulation stage,which is used as selecting condition for the elastic wave reverse-time imaging.Then,the elastic wave joint prestack reverse-time migration imaging condition and its key computational steps are presented in detail,and the elastic wavefield separation operators based on divergence and curl are introduced.Finally the joint reverse-time imaging of the multi-component elastic hybrid wave,pure P-wave and pure S-wave （converted-wave） is realized.The isotropic elastic model verifies the effect and correctness of the proposed first-arrival traveltime computing method.The numerical simulating experiment on anisotropic elastic medium model shows that the proposed elastic wave joint prestack reverse-time migration method can perfectly depict the complex variation of lithology and structure of geologic model.The imaging results coincide with theoretical and practical geological conditions.