Settlement Prediction In The Ulleung Basin Due To Gas Hydrate Production

초록

The potential existence of methane hydrate deposits in the Ulleung Basin of the Korean East Sea was suggested by the Korea Institute of Geoscience and Mineral Resources between 2000 and 2004 and a pilot production project is planned for 2015 as the world’s second offshore hydrate production project. The basin has a water depth of 1500-2300 m; however, the depth of the hydrate occurrence zone is relatively shallow (about 100-200 MBSF) for gas hydrate production. There is high potential for geomechanical stability problems such as marine landslides, seafloor subsidence, and wellbore instability. In this study, 2D axisymmetric numerical modeling is conducted to simulate gas hydrate production from the Ulleung basin by depressurization. The simulation incorporates the physical processes of hydrate dissociation, the pore fluid flow and the geomechanical response of hydrate-bearing sediments. During depressurization, deformation of sediments around a production well is generated by the pore pressure difference in the depressurized and dissociation region. This tendency becomes more pronounced due to a stiffness decrease of hydrate-bearing sediments caused by hydrate dissociation.