Practical issues of reverse time migration: true amplitude gathers, noise removal and harmonic-source encoding

Abstract

Recently, reverse-time migration (RTM) has drawn a lot of attention in the industry. Unlike one-way wave equation migration, RTM does not need to deal with the theory of singular pseudo-differential operators. A straightforward implementation of RTM correctly handles complex velocities and produces a complete set of acoustic waves (reflections, refractions, diffractions, multiples, evanescent waves, etc.). The RTM propagator also carries the correct propagation amplitude and imposes no dip limitations on the image. In the past, the strong migration artifacts and the intensive computational cost have been the two major problems that prevented RTM from being used in production. In this paper, we first formulate RTM based on inversion theory and then we address some solutions to suppress the low frequency migration artifacts. At the end, we propose harmonic-source migration as a way to improve the efficiency of delayed-shot RTM.