Theoretical analysis and numerical simulation of acoustic waves in gas hydrate-bearing sediments
Lin Liu(刘琳)1,2,3, Xiu-Mei Zhang(张秀梅)1,2,3,†, and Xiu-Ming Wang(王秀明)1,2,3
1 State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China; 2 University of Chinese Academy of Sciences, Beijing 100149, China; 3 Beijing Engineering Research Center of Sea Deep Drilling and Exploration, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
Abstract Based on Carcione-Leclaire model, the time-splitting high-order staggered-grid finite-difference algorithm is proposed and constructed for understanding wave propagation mechanisms in gas hydrate-bearing sediments. Three compressional waves and two shear waves, as well as their energy distributions are investigated in detail. In particular, the influences of the friction coefficient between solid grains and gas hydrate and the viscosity of pore fluid on wave propagation are analyzed. The results show that our proposed numerical simulation algorithm proposed in this paper can effectively solve the problem of stiffness in the velocity-stress equations and suppress the grid dispersion, resulting in higher accuracy compared with the result of the Fourier pseudospectral method used by Carcione. The excitation mechanisms of the five wave modes are clearly revealed by the results of simulations. Besides, it is pointed that, the wave diffusion of the second kind of compressional and shear waves is influenced by the friction coefficient between solid grains and gas hydrate, while the diffusion of the third compressional wave is controlled by the fluid viscosity. Finally, two fluid-solid (gas-hydrate formation) models are constructed to study the mode conversion of various waves. The results show that the reflection, transmission, and transformation of various waves occur on the interface, forming a very complicated wave field, and the energy distribution of various converted waves in different phases is different. It is demonstrated from our studies that, the unconventional waves, such as the second and third kinds of compressional waves may be converted into conventional waves on an interface. These propagation mechanisms provide a concrete wave attenuation explanation in inhomogeneous media.
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 11974018 and 11734017) and the Strategic Pilot and Technology Special Fund of the Chinese Academy of Sciences, China (Grant No. XDA14020303).
Lin Liu(刘琳), Xiu-Mei Zhang(张秀梅), and Xiu-Ming Wang(王秀明) Theoretical analysis and numerical simulation of acoustic waves in gas hydrate-bearing sediments 2021 Chin. Phys. B 30 024301
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