FULL WAVEFORM INVERSION IN TIME-LAPSE MODE USING SCATTERING THEORY

Full waveform inversion in time-lapse mode using scattering theory

Professor Morten Jakobsen

Associate Professor Einar Iversen

In order to monitor changes

Main

In the fluid saturations, stress and pore fluid pressure in a petroleum reservoir under production, one can compare seismic data corresponding to different time steps. Conventional time-lapse (or 4D) seismics is based on the analysis of changes in the travel times or seismic amplitude versus offset. However, one can potentially obtain more detailed information about production-induced changes in a petroleum reservoir by performing a full waveform inversion of time-lapse seismic data (Jakobsen and Ursin, 2011). The conventional adjoint state approach to full waveform inversion in the 4D as well as 3D case is very expensive computationally. However, by using a scattering theoretical approach, one can focus the inversion on a particular (4D) target of interest, under the assumption that the rest of the model is known (see Jakobsen and Ursin, 2015). The idea of using scattering theory for full waveform inversion method in time-lapse mode is not new (e.g., Muhumuza, 2015), but there are still plenty of room for further development of this promising approach.

In this study, the student should study the advantages and disadvantages of using different strategies for inverting time-lapse seismic waveform data. Also, the student should investigate the use of different scattering theoretical methods for reducing the computational cost of a full waveform inversion in time-lapse mode. The inversion methods and codes developed by the student in this project should be tested on synthetic data that have been contaminated with random noise to make the numerical experiments more realistic. 4D repeatability issues and other sources of uncertainty (model errors) should also be investigated.

Jakobsen, M. and Ursin, B., 2011. T-matrix approach to the nonlinear waveform inversion problem in 4D seismics. Expanded abstract, 73rd EAGE meeting, Vienna.

Jakobsen, M. and Ursin, B., 2015. Full waveform inversion in the frequency domain using direct iterative T-matrix methods. Journal of Geophysics and Engineering, 12, 400-418.

Muhumuza, K., 2015. Modelling and inversion of time-lapse seismic data using scattering theory. Master thesis, University of Bergen.

A. Asnaashari, R. Brossier, S. Garambois, F. Audebert, P. Thore and J. Virieux, 2015. Time-lapse seismic imaging using regularized full-waveform inversion with a prior model: which strategy? Geophysical Prospecting, 63, 78–98

This project requires a strong background in signal theory as well as wave propagation and  inversion. It will also be strictly required to have good skills or a talent for computer programming.