ESR2.1: Tianci CuiPhysical virtual sources by focusing

Tianci Cui obtained her B.Sc. in Exploration Geophysics from China University of Petroleum-Beijing in 2013. She joined the CREWES project (Consortium for Research in Elastic Wave Exploration Seismology) at the University of Calgary, Canada in September 2013. For her M.Sc. research, she worked with Dr. Gary Margrave on improving seismic-to-well ties. In December 2015, Tianci will be a Ph.D. student at Schlumberger Gould Research Center in UK. She will work on Marchenko redatuming with Dr. Ivan Vasconcelos. Fascinated by playing with physics and mathematics to understand the geology, Tianci is very looking forward to the three-year research training within the WAVES ITN.

Main host institution

Schlumberger Gould Research (Cambridge, UK)

Supervisor

Ivan Vasconcelos (IVasconcelos2 @ slb.com)

Secondment institution

Department of Geosciences and Engineering, Faculty of Civil Engineering, Delft University of Technology (Delft, Netherlands)

Objectives

Many recent studies in acoustics and seismology have shown how the impulse response (Green's function) of a medium can be reconstructed empirically, by averaging over time the cross- correlation of ambient signal recorded at two receivers (i.e., seismic interferometry, ambient-noise seismology). This approach is very powerful in that it allows to predict accurately the effects of a source placed at any of the receivers' locations; it is, on the other hand, limited to areas where receivers can actually be deployed: in practice, the outer surface of the medium. A new method has recently been devised to overcome this limitation. It is applicable to any medium bounded by at least one reflecting boundary. In this approach, dubbed "one-sided autofocusing" (or "Marchenko redatuming"), the response to a virtual source located anywhere within the medium can be reconstructed from records of reflected waves, if the medium is illuminated by sources outside it. So far, one-sided autofocusing has been implemented numerically in relatively simple models; the ESR will conduct futher numerical testing in highly complex models and verify experimentally (at ETH WaveLab) that physical sources can indeed be generated within a real medium by one-sided autofocusing. Furthermore, the ESR will focus on improving the current practice of Marchenko redatuming, to account for highly complex media (e.g., subsalt environments) and multicomponent fields (e.g., in elastic media). Finally, the ESR will study imaging and inversion approaches that are especially tailored to take full advantage of Marchenko redatuming, verifying them both numerically and experimentally.

Expected results:

One-sided autofocusing will be verified experimentally. Its applications will be explored, including, e.g., tuning of the virtual-source radiation pattern, or simulation, in a real medium, of arbitrary boundary conditions independent of the medium's actual boundaries. New findings will be employed to improve existing methodologies both for wavefield redatuming as well as imaging.

International conferences:

- EAGE - 79th European Association of Geoscientists & Engineers Conference & Exhibition 2017, 12-15/06/2017: abstract and poster on Marchenko redatuming of the hDVS signal

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further information:

Tianci Cui LinkedIn page