Summary
Through the multidimensional Marchenko equation, seismic redatuming can be expressed as a series. Unlike in conventional redatuming, where only the first term of these series is evaluated, not only primary reflections, but all orders of internal multiples are taken into account by this approach. By crosscorrelation of the redatumed wavefields with their corresponding (direct) source wavefields, as computed in a macro velocity model, a seismic image can be obtained without artifacts from internal multiples. Unfortunately, this approach requires accurate knowledge of the source signature, which is not always available. Moreover, the method is sensitive for source / receiver ghosts, coupling effects, attenuation and other noise. In practice, the individual terms in the series can also be added adaptively. This procedure is successful if internal multiples don’t interfere with primary reflections, but has its limitations in more complex media. In this contribution, we analyze the feasibility of adaptive addition, using only the first two terms in the series. The result appears useful for internal multiple suppression, as we illustrate on synthetic data with severe event interfererence and on field data.
Introduction
In Reverse Time Migration (RTM), seismic data are propagated backwards in time from the Earth’s surface to image points in the subsurface, using finite-difference computations in a smooth macro velocity model. An image is created by crosscorrelation of these backpropagated receiver wavefields with their associated source wavefields, which are propagated forwards in time from the source locations. An equivalent result can be obtained by redatuming the recorded data to every image point in the subsurface using pre-computed Green’s functions and crosscorrelating these redatumed data with their associated source wavefields (Esmersoy and Oristaglio, 1988; Schuster, 2002). Although RTM has been very successful in imaging primary reflections, it is not able to handle internal multiples, given that the macro model is generally smooth and does not contain information on the subsurface reflectivity. As a consequence, internal multiples are imaged at erroneous locations, causing artifacts in the RTM image.
