Public Defence: Xingguo Huang
Modeling and inversion of seismic data using multiple scattering, renormalization and homotopy methods.
Xingguo Huang had his PhD public defence on May 14, 2020. Here he presented his disseration:
"Modeling and inversion of seismic data using multiple scattering, renormalization and homotopy methods"
Seismic data are obtained when a pressure wave is sent into the Earth and the energy reflected at geological boundaries is recorded at the Earth’s surface. This principle is exactly the same as in medical ultrasound. When 3D seismic data are obtained at the same location at different times, the resulting data are referred to as 4D seismic data. Such data allow us to monitor how properties at a specific target area in the Earth’s subsurface changes with time. In the last couple of decades we have witnessed an increased use of 4D seismic data. Traditionally, the result of successful interpretation of 4D seismic data has been a better understanding of the oil saturation in the reservoir, leading to identification of the water-flooded areas and pockets of remaining oil, and an improved understanding of compartmentalization of the reservoir. The interpretation of the reservoir properties and dimensions are crucial when making decisions for drilling new wells.
Seismic scattering theory plays an important role in seismic forward modeling and is the theoretical foundation for various seismic imaging methods. Full waveform inversion is a powerful technique for obtaining a high-resolution model of the subsurface. In computational geophysics, many applications involve the use of seismic scattering theory. The Born scattering series is obtained by expanding the Lippmann-Schwinger equation in terms of an iterative solution based on perturbation theory. Such an expansion assumes weak scattering and may have the problems of convergence in strongly scattering media.
This dissertation presents work done on developing seismic forward modelling methods for strongly scattering and anisotropic media, efficient methods for time-lapse full waveform inversion and estimation of uncertainty and multiparameter trade-offs in anisotropic elastic full waveform inversion based on integral equation approaches and the iterated extended Kalman-filter.
llustration of full waveform inversion. Top left: True model. Bottom left: Initial model guess. Right: Examples of how full waveform inversion improves the initial model guess so that it approaches the true model.