An overview of depth imaging in exploration geophysics

Abstract

Prestack depth migration is the most glamorous step of seismic processing because it transforms mere data into an image, and that image is considered to be an accurate structural description of the earth. Thus, our expectations of its accuracy, robustness, and reliability are high. Amazingly, seismic migration usually delivers. The past few decades have seen migration move from its heuristic roots to mathematically sound techniques that, using relatively few assumptions, render accurate pictures of the interior of the earth. Interestingly, the earth and the subjects we want to image inside it are varied enough that, so far, no single migration technique has dominated practical application. All techniques continually improve and borrow from each other, so one technique may never dominate. Despite the progress in structural imaging, we have not reached the point where seismic images provide quantitatively accurate descriptions of rocks and fluids. Nor have we attained the goal of using migration as part of a purely computational process to determine subsurface velocity. In areas where images have the highest quality, we might be nearing those goals, collectively called inversion. Where data are more challenging, the goals seem elusive. We describe the progress made in depth migration to the present and the most significant barriers to attaining its inversion goals in the future. We also conjecture on progress likely to be made in the years ahead and on challenges that migration might not be able to meet.

Correlation-based seismic velocity inversion

“…The exact conditions under which the normal operator is invertible have been extensively studied (Beylkin, 1984(Beylkin, , 1985ten Kroode et al, 1998;Stolk & de Hoop, 2006;de Hoop et al, 2009). Next, we will briefly review several methods that can be used to obtain an approximate solution of the linearized inverse problem, while we refer to Etgen et al (2009) for an extensive, up-to-date overview of migration methods.…”

Understanding the reverse time migration backscattering: noise or signal?

“…salt bodies), and strong lateral variations. The reason for the RTM success is that a wavefield reconstructed with the two-way operator can easily handle any dip, multi-pathing, and reflections from steep structures (Etgen et al, 2009;Gray et al, 2001).…”

Source‐receiver two‐way wave extrapolation for prestack exploding‐reflector modeling and migration

“…Wave-equation depth migration methods are commonly divided into two types: one-way for wave extrapolation in depth and two-way for wave extrapolation in time or reverse-time migration (Biondi, 2006;Etgen et al, 2009). Conventionally, both methods are applied on individual shot gathers.…”