Editorial Comment: A brighter future for methane hydrates?

Methane hydrates are three-dimensional ice-lattice structures in which natural gas is trapped. These hydrates are found both onshore and offshore, in ocean sediments along continental shelves and underneath the Arctic permafrost. When the hydrates are melted into water, methane molecules are released. The U.S. Geological Survey estimates that worldwide gas hydrates reserves are between 10 times and 100 times more plentiful than U.S. shale gas reserves, which are estimated at more than 342 Tft³ as of 2018.

However, the recovery of methane hydrates has been difficult, as the gas is locked in permafrost and often located in deepwater coastal areas. The high pressure that helps form methane hydrates must be maintained when the sediment cores are analyzed, or the hydrates will dissociate into water and gas. Also, concerns exist about how the potential release of methane emissions during hydrates extraction could impact the environment.

However, researchers recently announced a technological breakthrough that could boost the amount of methane hydrates recovered from permafrost, while decreasing the amount of greenhouse gas released into the atmosphere. An international team of researchers from Skoltech University in Russia and Heriot-Watt University in Scotland found that replacing the methane in the hydrates with flue gas from fuel combustion allowed for more efficient recovery of methane from permafrost.

An additional benefit of the process is the potential to use methane hydrates as carbon sinks. By locking flue gas in permafrost, the amount of greenhouse gas released into the atmosphere can be limited while simultaneously preventing the spontaneous release of methane. The research team used a CO₂-based hydrate in flue gas to replace the methane hydrate, which allowed them to capture nearly 82% of the CO₂ in the flue gas.

The study, published in November 2019 in Scientific Reports, stated, “In comparison with potential methods such as thermal stimulation, depressurization or chemical inhibitor injection, CO₂ or CO₂-mixed gases (e.g., flue gas) injection is more environmentally friendly because of the potential to capture CO₂ simultaneously with methane recovery.”¹

The new method could help Russia exploit its newly discovered oil and gas reserves in the Arctic, which have the potential to accidentally release significant quantities of trapped methane into the atmosphere. The emissions risk, along with a lack of infrastructure in the remote areas, is hindering Russia’s development of its Arctic reserves.

Japan is also targeting commercial production of methane hydrates—as much as 40 Tft³—although full-scale development of these resources is not expected to be achievable in the near term. The country is studying ways to control methane release from ice so that the gas flows directly into the production well, thereby maximizing the resource potential and minimizing the risk of rogue emissions. GP

Literature cited

1. Hassanpouryouzband, A. et al., “An experimental investigation on the kinetics of integrated methane recovery and CO₂ sequestration by injection of flue gas into permafrost methane hydrate reservoirs,” Scientific Reports,  Vol. 9, November 7, 2019.