Abstract

Methane hydrate is a solidified form of methane gas and has been attracting an international interest because of its potential as an alternative energy resource. It is believed to reside throughout the globe in formations beneath areas of permafrost or deep under seabed. Such sites provide conditions for hydrate to exist: low temperature and high pressure. For methane gas production from methane hydrate soils, the phase equilibrium condition has to be artificially shifted (i.e. hydrate dissociation) either by injection of heat energy or by depressurisation of pore water. However, through a dissociation process, geomechanical problems such as submarine landslide and wellbore instability may arise due to the fact that formation stiffness and strength reduce as hydrate dissociates.

This talk presents the overview of a coupled thermo-hydro-mechanical formulation, a constitutive model for hydrate-bearing sediments, and its application to the field methane gas production trials by a depressurisation method that conducted at the Mallik site, Canada in 2007 and 2008.