SUPPRESSING THE LOW-FREQUENCY NOISE IN REVERSE-TIME MIGRATION UTILIZING THE NON-REFLECTING WAVE EQUATION

摘要

As a high-precision geophysical imaging method, reverse-time migration (RTM) iswidely used in seismic exploration. However, the imaging quality in RTM is susceptibleto low-frequency noise, which is chiefly caused by unwanted cross-correlation ofreflections. In order to remove the low-frequency noise, the non-reflecting wave equationcan be introduced to RTM. On this basis, we propose an improved RTM methodutilizing the non-reflecting wave equation to achieve low-frequency noise suppression inprestack acoustic RTM. Specifically, the non- reflecting wave equation is only used inthe process reverse- time wavefield simulation, to take advantage of its ability ofweakening reflections. Accordingly, abnormal imaging points attributable to reflectionscan be reduced. We evaluated the denoising effect through numerical examples includinga simple layered model, a concave model, and the complicated Marmousi model. Theresults show that low-frequency noise can be effectively suppressed by introducing thenon-reflecting wave equation into RTM. This improved RTM method can achieve betterimaging with less low-frequency noise compared with conventional RTM method.Moreover, the improved RTM method ensures computational efficiency withoutincreasing storage demands.