表面多次波和有效波联合成像

Simultaneous reverse time migration primaries and free-surface related multiples

常规逆时偏移仅利用有效波进行成像,将表面多次波视为噪声压制掉.然而,表面多次波提供的额外地下反射信息能够用于偏移成像,提升成像范围.本文提出了一种表面多次波和一次反射波联合逆时偏移成像方法,它无需预测或分离表面多次反射波,能够对一次反射波和表面多次波直接成像.本文分别对水平层状模型和Sigsbee 2B模型进行了联合逆时偏移成像测试,结果表明,相对于常规有效波逆时偏移成像,所提出的联合逆时偏移方法能够提供额外的构造信息,基于一次波和表面多次波联合逆时偏移的成像方法能够对复杂地下构造准确成像.

Conventional RTM only uses primaries, however, free-surface related multiples can sometimes provide extra illumination of the sub-surface, and this information could be used in migration procedures. There are many migration methods using free-surface related multiples, but most approaches need to predict multiples. There is a new RTM approach that uses the primaries and the free-surface related multiples simultaneously. the proposed approach can provide comparable migration results and does not need multiple predictions. The source function was recorded field data including primaries and free-surface related multiples, together with a synthetic wavelet;the back-feild were field data with complete recorded. The imaging condition of the proposed approach was the same as the crosscorrelation imaging condition of conventional RTM. A layer velocity model with scatterers and the Sigsbee 2 B synthetic data set were used for numerical experiments. The numerical results showed that the proposed approach can cover a wider range of the subsurface and provide better illumination compared with conventional RTM. The proposed approach was easy to implement and avoided tedious multiple prediction;it might be significant for general complex subsurface imaging.