An influence of boundary conditions on initiation of gas blowout in permeable rock

Abstract

Free gas in permafrost may originate from dissociating methane hydrates are widespread in the Arctic region. Methane can migrate through sand-clay permafrost and accumulate there, especially in sand beds. Gas migration is often accompanied by the formation of pressurized zones. As the pressure reaches some critical value, the overburden breaks down, and methane releases explosively with formation of craters on the seabed. In the paper, gas migration is simulated in 2D, with implications for the conditions at which 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 the Hele-Shaw cell and with field data. The presented results should be taken into account when estimating the aftereffects of the methane hydrates dissociation due to global warming or due to surface condition changes.