Optimal full waveform inversion strategy for marine data in azimuthally rotated elastic orthorhombic media

Optimal full waveform inversion strategy for marine data in azimuthally rotated elastic orthorhombic media

Ju-Won Oh and Tariq Alkhalifah, “Optimal full waveform inversion strategy for marine data in azimuthally rotated elastic orthorhombic media”, Geophysics 83 (2018): R307-R320. doi: 10.1190/geo2017-0762.1​
Ju-Won Oh, Tariq Alkhalifah
ull-waveform inversion, rotated orthorhombic media, hierarchical parameterization, radiation-pattern analysis, fracture direction
2018
​The orthorhombic anisotropic description of Earth layers can allow the capture many of the Earth’s anisotropic complexity. The inversion for high-resolution azimuthal variation of anisotropy is important for reservoir characterization, among other applications. A high-resolution description of the azimuth of fractures can help us predict flow preferences. To verify the feasibility of multi-parameter full waveform inversion for marine data assuming azimuthally rotated elastic orthorhombic media, we analyze the radiation patterns and gradient directions of orthorhombic parameters to the reflection data. We first express the gradient direction of the orthorhombic parameters considering the azimuthal rotation of the symmetric planes. Then, to support our observations in the gradient direction, the radiation patterns of the partial derivative wavefields from each parameter perturbation are also derived under the rotated elastic orthorhombic assumption. To find an optimal parameterization, we compare three different parameterizations: monoclinic, velocity-based and hierarchical parameterizations. Then, we suggest an optimal multi-stage update strategy by analyzing the behavior of the rotation angle as an FWI target. To analyze the trade-off among parameters in different parameterizations, we calculate the gradient direction from a hockey puck model, in which each parameter is perturbed at the different location on a horizontal layer. The trade-off analysis supports that the hierarchical parameterization provides us with more opportunities to build up subsurface models with less trade-off between parameters and less influence of the azimuthal rotation of orthorhombic anisotropy. The feasibility of the proposed FWI strategy is examined using synthetic marine streamer data from a simple 3D reservoir model with a fractured layer.
(print): 0016-8033 (online): 1942-2156