Study of the critical gas saturation during methane hydrate dissociation at the single-pore scale: Analytical solutions for large pores

Abstract

Offshore/onshore deposits of methane hydrates could represent a large potential future source of energy, provided the difficulties associated with their safe, environmental-friendly and economically-viable production can be resolved adequately. Examining hydrate dissociation at different length scales (e.g., molecular, single pore, pore network, core and field) is part of the goal to initially identify, and subsequently address such difficulties. The current study introduces a mathematical-modeling approach and is focused on the evolution of methane gas that occurs within a single pore and is the result of the dissociation of methane hydrate that was originally deposited within the pore. We examine the critical gas saturation, which is defined as the fraction of gas volume inside a single pore when a spherical gas bubble reaches the pore walls for the first time. Further, we obtain critical values for pore sizes above which the production of methane gas is possible. The results shown here correspond to the case of large pores where the depression of the dissociation temperature (due to the presence of small-sized pores) is ignored.