Influence of boundary conditions on initiation of gas blowout in permeable rock Available to Purchase

Free gas in permafrost may originate from dissociating methane hydrates that are widespread in the Arctic region. Methane can migrate through sand–clay permafrost and accumulate there, particularly in sand beds. Gas migration is often accompanied by the formation of pressurised zones. As the pressure reaches some critical value, the overburden breaks down, and methane is released explosively with formation of craters on the seabed. In this paper, gas migration is simulated in two dimensions, with implications for the conditions under which an increased gas flow rate can lead to failure of granular rocks, as well as for the place of blowout initiation depending on boundary conditions. The paper shows that the location of sediment blowouts in the presence of an impermeable lid or obstacle differs from the location of blowouts without them. The paper also shows that the type of pressure source (homogeneous or heterogeneous) also affects the location of the blowout initiation. The numerical results are in good agreement with laboratory experiments carried out in a sandy medium at a Hele-Shaw cell and with field data. The presented results should be taken into account when estimating the after-effects of methane hydrate dissociation due to global warming or due to surface condition changes.