Reverse time migration of multiples for subsalt imaging

Abstract

Some hydrocarbon reservoirs are trapped beneath salt bodies, where seismic imaging is greatly challenged due to poor illumination. Multiple reflections have different propagation wave paths from primary reflections and thus can be used to complement the illuminations where primary reflections from beneath the salt are not acquired. Consequently, migration of multiples can sometimes provide better subsalt images compared to conventional migration which uses primary reflections only. In this paper, we propose to modify conventional reverse time migration so that multiples can be used as constructive reflection energy for subsalt imaging. This new approach replaces the impulsive source wavelet with the recorded data containing both primaries and multiples and uses predicted multiples as the input data instead of primary reflections. In the reverse time migration process, multiples recorded on the surface are extrapolated backward in time to each depth level, and the observed data with both primaries and multiples are extrapolated forward in time to the same depth levels, followed by a crosscorrelation imaging condition. A numerical test on the Sigsbee2B data set shows that a wider coverage and a more balanced illumination of the subsurface can be achieved by migration of multiples compared with conventional migration of primary reflections. This example demonstrates that reverse time migration of multiples might be a promising method for complex subsalt imaging.

An excitation potential imaging condition for elastic reverse time migration

“…Soon after, McMechan (1986, 1990) developed and applied the RTM to the prestack sections. However, the conventional RTM is usually based on the acoustic wave equation (Baysal et al, 1983;Liu et al, 2011) and is simply an approximation of the elastic wave equation. It ignores the shear-wave mode, which often leads to the incorrect characterization of wave propagation, incomplete illumination of the subsurface, and poor amplitude characterization (Yan and Sava, 2008).…”

Elastic P- and S-wave autofocus imaging with primaries and internal multiples

“…Youn and Zhou (2001) devised a prestack depth migration method that used a model-based estimate of the internal multiples. Data-driven methods for imaging using internal multiples include least squares migration (Brown and Guitton, 2005), interferometric imaging (Jiang et al, 2005), one-way wave equation migration (Malcolm et al, 2009), full wavefield migration (Berkhout, 2012), RTM for internal multiples (Liu et al, 2011;Fleury, 2013) and generalized internal multiple imaging (Zuberi and Alkhalifah, 2014).…”

Efficient anisotropic quasi-Pwavefield extrapolation using an isotropic low-rank approximation

“…We next apply the proposed method in a Reverse Time Migration (RTM) algorithm Liu et al 2011). We use the same wavelet and sampling as the previous test, and we evenly deploy 70 shots and 150 receivers on the surface of the model.…”