Abstract
Crosswell seismic measurements enable obtaining high resolution, high accuracy images of the subsurface between boreholes. They are, however, generally expensive considering the need of deployment of special downhole sources. In this study, we develop a novel nonlinear waveform inversion to estimate velocity structures between two vertical boreholes using VSP data without downhole sources. Contrary to the conventional full waveform inversion (FWI), the effect of wave propagation between surface sources and one of the vertical boreholes is appropriately cancelled using representation theory. Furthermore, it enables us to calculate partial derivatives of the cost function without explicitly resolving the Green’s functions in seismic interferometry. We test numerically this new approach of time-lapse monitoring of a deeper target layer, considering also the effect of changes in the complex, shallow vadose zone. We assume that the temporal changes in velocity in the vadose zone are larger than those at the deeper target layer. Our results show that in contrast to conventional FWI, the newly developed approach has the advantages of expensive crosswell seismics involving downhole sources. The estimated velocity is robust against spatiotemporal changes in the near-surface. The approach will be very useful when accurate time-lapse seismic measurements are needed in a cost-effective manner.
Original language | English |
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Title of host publication | Fifth EAGE Workshop on Borehole Geophysics |
Subtitle of host publication | 18 -20 November 2019, The Hague, Netherlands |
Publisher | EAGE |
Pages | 1-5 |
Number of pages | 5 |
Publication status | Published - 2019 |
Event | 5th EAGE Workshop on Borehole Geophysics: Bridging The Gap Between Surface And Reservoir - The Hague, Netherlands Duration: 18 Nov 2019 → 21 Nov 2019 https://eage.eventsair.com/borehole-geophysics2019/ |
Conference
Conference | 5th EAGE Workshop on Borehole Geophysics |
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Country/Territory | Netherlands |
City | The Hague |
Period | 18/11/19 → 21/11/19 |
Internet address |