Reverse Time migration Based on Internal Multiples

Abstract:

Internal multiples are waves reflected more than once at interfaces before reach to the surface receivers. Internal multiples are usually generated below coal seams, salt domes, basalt and igneous rocks with high velocity contrast, and behave differently compared to primary reflections and surface-related multiples. Internal multiple reflections have different propagation paths compared with primary reflections and surface-related multiples, thus can complement illuminations where other waves are unavailable. We propose a novel approach to image structures with internal multiples. With this method, internal multiples are separated and used as data for reverse time migration. Instead of applying image condition directly to the source and receiver waves, we decompose both source and receiver waves extrapolated into up- and down-going waves. Then apply the image condition to up-going source and receiver waves to form an up-up image, and apply to down-going source and receiver waves to form a down-down image. We use a similarity analysis to compare the up-up and down-down images, and separate true images from artifacts. Numerical examples with simple velocity models are used to demonstrate how to construct up-up and down-down image conditions and eliminate migration artifacts. Finally, we test the 2D SMAART JV model with salt structures for migration using internal multiples.

ACKNOWLEDGEMENTS

 The research was funded by the National Nature Science Foundation of China (Grant No. 41430321, 41374138). We would thank SMAART JV consortium for offering SMARRT data.