Target-enclosing interferometric redatuming: can we turn one-sided illumination into two-sided illumination?

Joost van der Neut
PhD Candidate
Delft University of Technology

To create a seismic image of a target reflector in the subsurface, data should be collected from a variety of source and receiver locations. Ideally, these locations should completely surround the target, providing illumination from each possible angle (Oristaglio, 1989). In practice, seismic sources and receivers are generally situated at the Earth's surface only, providing so-called one-sided illumination. Conventional linear imaging methods utilize primary-scattered waves only that - when illuminating a complex medium from one side only - do not penetrate everywhere, leaving shadow zones in the image. In many cases, these shadow zones are illuminated by multiple-scattered waves though. Unfortunately, multiple-scattered waves are notoriously difficult to image without generating undesired artifacts (e.g. Malcolm et al., 2011). New developments in and beyond seismic interferometry might allow us to reorganize seismic data, such that multiple-scattered waves are easier to interpret and to image. Using interferometry, it has already been shown that virtual sources can be generated at physical receiver locations by focusing multiple-scattered waves (Schuster, 2009). Recently, it was demonstrated by Broggini et al. (2012) and Wapenaar et al. (2012) that virtual sources can also be generated in the absence of local receivers at the focal points. Inspired by these developments, I have started to work on a method to transform conventional data with sources and receivers at the Earth's surface into virtual data as if sources and receivers are located above and below a selected target zone in the subsurface. The method consists of two sequential steps: 1) wavefield focusing, using a scheme that is currently being developed by Wapenaar et al. (2012) and 2) target-enclosing interferometric redatuming (TEIR), which I will introduce in this presentation.

Input data of TEIR are the full transmission responses with sources at the Earth's surface and receivers at two depth levels, being located above and below the target zone. In practice, these responses should be generated by the wavefield focusing method of Wapenaar et al. (2012). Output data are reflection and transmission responses as if virtual sources and receivers are located above and below the target zone. The method is based on inverting a series of multi-dimensional equations of the convolution- and the correlation-type. TEIR brings two major advantages compared to conventional interferometric redatuming (in which a single multi-dimensional equation is inverted, see Wapenaar and van der Neut, 2010): 1) the virtual sources illuminate the target from two sides and 2) all reflections from outside the target zone are eliminated. The generated data can be processed like conventional data, but various benefits are obtained: 1) since multiple-scattered waves are exploited, seismic shadows can be illuminated; 2) the data volume is reduced significantly, saving dramatically on computational resources, when applying TEIR in conjunction with advanced processing methods such as least-squares migration or full-waveform inversion; 3) if a shallow section of the subsurface is strongly heterogeneous, wave propagation through this section can be eliminated from the data by generating virtual sources and receivers below it; 4) changing rock properties can be monitored locally in the target zone, independent of changes that occur elsewhere in the subsurface.

References

- Broggini, F., Snieder, R. and Wapenaar, K., 2012, Focusing the wavefield inside an unknown 1D medium, Geophysics, 77, A25-A28.
- Malcolm, A. E., de Hoop, M. V. and Ursin, B., 2011, Recursive imaging with multiply scattered waves using partial image regularization: a North Sea case study, Geophysics, 76, 33-42.
- Oristaglio, M. L., 1989, An inverse scattering formula that uses all the data, Inverse Problems, 5, 1097-1105.
- Schuster, G. T., 2009, Seismic interferometry: Cambridge University Press.
- Wapenaar, K. and van der Neut, J., 2010, A representation for Green's function retrieval by multidimensional deconvolution: Journal of the Acoustical Society of America, 128, EL366-EL371.
- Wapenaar, K., Thorbecke, J., van der Neut, J., Slob, E., Broggini, F., Behura, J. and Snieder, R., 2012, Integrated migration and internal multiple elimination, SEG Annual Meeting, expanded abstracts (accepted).

sep/seminar/abstracts/jvdneut.txt · Last modified: 2015/05/27 02:06 (external edit)
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