Recovery of Methane from Gas Hydrates Intercalated within Natural Sediments Using CO₂ and a CO₂/N₂ Gas Mixture

Abstract

The direct recovery of methane from massive methane hydrates (MHs), artificial MH-bearing clays, and natural MH-bearing sediments is demonstrated, using either CO(2) or a CO(2)/N(2) gas mixture (20 mol % of CO(2) and 80 mol % of N(2), reproducing flue gas from a power plant) for methane replacement in complex marine systems. Natural gas hydrates (NGHs) can be converted into CO(2) hydrate by a swapping mechanism. The overall process serves a dual purpose: it is a means of sustainable energy-source exploitation and greenhouse-gas sequestration. In particular, scant attention has been paid to the natural sediment clay portion in deep-sea gas hydrates, which is capable of storing a tremendous amount of NGH. The clay interlayer provides a unique chemical-physical environment for gas hydrates. Herein, for the first time, we pull out methane from intercalated methane hydrates in a clay interlayer using CO(2) and a CO(2)/N(2) gas mixture. The results of this study are expected to provide an essential physicochemical background required for large-scale NGH production under the seabed.

Review of natural gas hydrates as an energy resource: Prospects and challenges

“…The feasibility of injecting flue gas has been tested and affirmed in laboratory scale as well as field scale as highlighted in previous chapters [243,244]. The direct injection of flue gas eliminates the steps to concentrate CO 2 , thereby increasing the economic feasibility of the guest-exchange process.…”

Replacement micro-mechanism of CH4 hydrate by N2/CO2 mixture revealed by ab initio studies

“…Recently, nitrogen has been explored as a replacement promoter that can greatly improve the CH 4 recovery rate [25][26][27][28]. Park and coworkers [27] have experimentally estimated an 85% CH 4 recovery rate when exposing the methane hydrate to the N 2 /CO 2 gas mixture.…”

Influence of gas sweep on methane recovery from hydrate-bearing sediments

“…Using this mode, the hydrate decomposition by hot water or inhibitor injection has been investigated (Koh et al, 2012;Yuan et al, 2013). In this work, the batch injection mode was also extended to hydrate recovery by N 2 sweep.…”

“…Compared with gas or liquid CO 2 replacement, methane recovery driven by gas mixture, for example, CH 4 -N 2 /CO 2 (Park et al, 2006;Koh et al, 2012), CH 4 -air or CH 4 -CO 2 /air (Kang et al, 2014), has been investigated and seem to be more feasible in terms of cost and environmental protection, which had also been adopted by US DOE in 2012 to verify the capacity of CH 4 -CO 2 replacement by injecting N 2 (77%) þCO 2 (23%) into hydrate-bearing sediments at Ignik-Sikumi field (NETL, 2012). However, at the initial stage of gas injection, gas mixtures would diffuse in hydrate reservoir firstly, rather than replace with methane immediately.…”