| Abstract: | Cancelling of multiple reflections by CDP stacking is generally incomplete. When the order of coverage is low, an improvement may be obtained by the use of special filters (e.g. Schneider et al: Geophysics 1965; D'Hoeraene: Geophysics 1966). But when the order of coverage is high, the efficiency of these filters is less obvious. On the other hand, the higher the order of coverage, the higher the efficiency in the solution presented. Schematically, our method includes three steps: Firstly: Searching for the multiple reflections. For this purpose Move Out corrections corresponding to the multiples are applied to each individual record, then CDP stacking is carried out. Secondly: Cleaning up of the individual records. “Decorrections” are firstly applied, then multiples are subtracted. For this, subtraction is weighed versus the energy of the multiples, that is to say versus the correlation between the original record and the pure multiple reflections. Thirdly: Normal processing with the cleaned records which have been obtained. The different steps of this method are illustrated with the help of theoretical examples. Its efficiency improvement in regard to normal CDP stacking is then demonstrated by means of true examples. |
