On the Impact of Incorrect Top-salt Interpretations on RTM

Abstract

We present a modeling study for reverse-time migration (RTM) imaging for different interpretations of the top salt boundary. The top salt is represented either as a rough surface or as a plane with a single anomaly resembling a syncline or an anticline. The focus of our analysis is the coherency and illumination of the underlying flat reflectors, given the true model and a set of perturbations from the true model. The perturbations are aimed at representing interpretations of the top salt boundary. One of our main findings is that an RTM image using the correct top salt model, but shifting it horizontally, diminishes the illumination and continuity of the underlying reflectors more than using a flat reflector. The RTM image of a syncline anomaly using an incorrect interpretation resembles an anticline, which can considerably affect the top salt picking and further refinements in its interpretation. In the models studied, we also find that changes in the vertical amplitude of the anomaly or of the roughness are more forgiving than changes in the width of the anomaly or in the frequency or the rugosity.