Title: A seepage-stress coupled analysis of seabed deformation induced by the decomposition of gas hydrate

Authors: Zhenwei Zhao; Xinchun Shang

Addresses: Civil Engineering Department, Fujian University of Technology, No. 3, Xueyuan Road, Fuzhou, China. ' Department of Mathematics and Mechanics, University of Science and Technology Beijing, No. 30, Xueyuan Road, Haidian District, Beijing, China

Abstract: The deformation of seabed considering seepage-stress coupling is analysed using finite element method in this study, the effect of the varying pore pressure on stress field is accounted in the analysis, and the impact of reservoir permeability and the well pressure on the decomposition radius is studied. The changes of mechanical parameters due to hydrate decomposition are achieved by using user defined field subroutine. The results show that vertical and horizontal effective stress of soil in the dissociated area increase significantly while gas hydrates are decomposed by depressurisation. The reservoir permeability and well pressure have significant impact on the decomposition radius. The seabed deformation increases non-linearly with the increasing of the gas hydrate decomposition radius. The maximum vertical displacement reaches 18 m and the maximum horizontal displacement reaches 7.5 m.

Keywords: gas hydrates; vertical wells; seabed deformation; pore pressure; well pressure; depressurisation; settlement; horizontal displacement; stress field; seepage; finite element method; FEM; reservoir permeability; permafrost; deep ocean sediments; sediment; offshore platforms; gas production.

DOI: 10.1504/IJCSE.2011.043922

International Journal of Computational Science and Engineering, 2011 Vol.6 No.4, pp.249 - 254

Available online: 25 Nov 2011

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