Creating Virtual Sources Inside an Unknown Medium from Reflection Data - A New Approach to Internal Multiple Elimination

Abstract

SUMMARYIt has recently been shown that the response to a virtual source in the subsurface can be derived from reflection data at the surface and an estimate of the direct arrivals between the virtual source and the surface. Hence, unlike for seismic interferometry, no receivers are needed inside the medium. This new method recovers the complete wavefield of a virtual source, including all internal multiple scattering. Because no actual receivers are needed in the medium, the virtual source can be placed anywhere in the subsurface. With some additional processing steps (decomposition and multidimensional deconvolution) it is possible to obtain a redatumed reflection response at any depth level in the subsurface, from which all the overburden effects are eliminated. By applying standard migration between these depth levels, a true amplitude image of the subsurface can be obtained, free from ghosts due to internal multiples. The method is non-recursive and therefore does not suffer from error propagation. Moreover, the internal multiples are eliminated by deconvolution, hence no adaptive prediction and subtraction is required.

Creating a virtual source inside a medium from reflection data: heuristic derivation and stationary-phase analysis

“…Since no actual receivers are needed inside the medium, virtual sources can be created anywhere. The virtual‐source responses contain the correct internal multiples, which can be used to improve seismic imaging and suppress the internal multiple ghosts (Wapenaar et al 2012). Because the created virtual sources are independent of each other, the prediction and removal of internal multiples will not suffer from error propagation, unlike other imaging methods that aim at internal multiple suppression.…”

Creating a virtual source inside a medium from reflection data with internal multiples: a stationary-phase analysis

“…We proposed a generalization to 2D of the model-independent wavefield reconstruction method of Broggini et al (2011Broggini et al ( , 2012b. The proposed data driven procedure yields the response to a virtual source and reconstructs correct internal multiples, without needing a receiver at the virtual source location and without needing detailed knowledge of the medium.…”

“…Since no actual receivers are needed inside the medium, virtual sources can be created anywhere. The virtual-source responses contain all internal multiples, hence the method could be used as a basis for imaging without internal multiples (Wapenaar et al, 2012b).…”

“…Controlled-source interferometric methods (Curtis et al, 2006;Bakulin and Calvert, 2006;Schuster, 2009) allow us to retrieve such a response without the need to know the medium parameters, but these methods require a receiver at the location of the virtual source in the subsurface and assume the medium is surrounded by sources. Our new approach removes the constraint of having a receiver at the virtual source location and is based on an extension of the 1D theory proposed earlier (Broggini et al, 2011(Broggini et al, , 2012bBroggini and Snieder, 2012) 1 . They show that, given the reflection response of a 1D layered medium, it is possible to reconstruct the response to a virtual source inside the medium, without having a receiver at the virtual source location and without knowing the medium.…”