Geotechnical and Geophysical Properties of Deep Marine Sediments Recovered from the Gas Hydrate Occurrence Regions in Ulleung Basin, East Sea, Korea

Abstract

The vast amounts of gas hydrate reserves have drawn scientific attentions as a potential energy resource. For gas hydrate production, gas hydrate-bearing sediments should be depressurized below the gas hydrate equilibrium pressure. The depressurization of a gas hydrate reservoir can lead to several geotechnical problems such as the destabilization of the production well, settlement of the seafloor installation, or slope failure of the production site. Thus, it is important to determine the geotechnical characteristics of gas hydrate-bearing sediments. This study determined the geotechnical and geophysical properties of deep marine sediments in Ulleung Basin, East Sea using minimally disturbed natural samples retrieved during the Second Ulleung Basin Gas Hydrate Expedition (UBGH2). Conventional geotechnical engineering test characterize the sediments highly plastic silty soils; they exhibited low hydraulic conductivities, and high compressibility when subjected to an increase in effective stress. It is expected that depressurization during gas hydrate production at the investigated sites would cause a significant amount of compaction around the production hole. In addition, the prior occurrence of gas hydrates in the samples was verified through a comparison of water content, compressibility, and electrical resistivity.