FUNDAMENTAL UNDERSTANDING OF THE KINETIC BEHAVIOUR OF METHANE HYDRATE FORMATION AND DISSOCIATION IN SANDY MEDIA

Abstract

Methane hydrates (MH) has been considered as the future source of energy because of its large resource volume and high energy storage capacity. To recover energy from MH-bearing sediments (MHBS) effectively and safely require a fundamental understanding of the dynamic behaviour of MH in sandy media. In this thesis, the dynamic behaviour of MH formation and dissociation was examined by combining the approach of both experimental observation and numerical simulation with validation. A comprehensive review of the kinetic models identified that heat transfer, fluid flow through porous media and the kinetic reaction rate of MH are the three controlling mechanisms in the processes of MH formation, dissociation and fluid production. A detailed numerical analysis was conducted on (a) the multi-step MH formation process and (b) the dissociation process under depressurization by coupling the thermo-hydraulic-chemical (T-H-C) effects. The simulation results were validated by experimental observations through a history-matching technique. Key thermophysical properties of MHBS and the associated kinetic rate parameters were estimated and the impending issue of phase spatial heterogeneity in synthesized MHBS were identified. A subsequent sensitivity analysis was conducted to identify the relative importance of key transport parameters on the production of gas and water during depressurization.