Multiple Attenuation On Shot Gathers Using Radon Transform

Multiple attenuating is a long-standing problem in seismic data processing. A several of techniques along with their problems on multiple suppressing are reviewed. The characteristics of multiple reflections on shot gathers are systematically analyzed. A new multiple attenuation method is presented in this thesis. Based upon the ideas of event realigning and adaptive energy removal of multiples, the approach can directly eliminate reverberations on shot gathers using the linear or parabolic Radon transforms.The conventional multiple attenuation techniques using Radon transform are usually involved first in stacking velocity estimation of primary or multiple reflections, and then filtering multiple reflections on CMP gathers. Obviously, the accuracy of velocity analysis affects much to the performance of multiple suppressing. However, multiple reflections usually tamper with the accuracy of velocity analysis, and as a result, good performance of multiple suppressing cannot be achieved in such a case. Different from the conventional techniques that are applied on CMP gathers the new method presented in this thesis is directly applied on shot gathers. The events of reverberations on a shot gather are found using accurate ray tracing. The shot gather is then divided into different reasonable time windows according to the traced time-distance curves of reverberations. Within each time window, a multiple event is aligned to be horizontally flat. The primary reflections will not be flat since they have different apparent velocities. A linear or parabolic Radon method with adaptive muting of multiple energy, is used to filter the reverberations in the given time window. The filtered data are then re-aligned back to the original shot gathers to complete the multiple suppressing for this shot gather.Test results demonstrate that the method presented in this thesis is better noise-resistant. It is robust for eliminating the reverberations on shot gathers. The approach may also be used for other regular noise suppressing on both shot and CMP gathers.