Wavefield reconstruction methods for reverse time migration

Abstract

During pre-stack reverse time migration (RTM), the shot and receiver wavefields are extrapolated separately along opposite directions, which means the shot wavefield should be saved and it is a bottleneck of RTM. The random boundary condition (RBC) method could be used to reconstruct the shot wavefield to solve this problem. The disadvantage of RBC is that the free surface boundary condition (FSBC) should be used because the RBC at the surface boundary will induce severe noise all through the imaging profile. The use of FSBC is also harmful because the reflections from the surface will generate imaging illusions. In this paper, we use two different boundary conditions, which use an absorbing boundary condition on the upper boundary, to perfectly reconstruct the shot wavefield. The new schemes could solve the free surface boundary problem and would not demand much memory. The numerical examples prove the efficiency of these methods. © 2013 Sinopec Geophysical Research Institute.