Failed Methods
After two decades of study, technologies from major
oil companies and governments still can’t produce methane from gas hydrates,
safely and economically
The documented methods currently available for producing methane from oceanic gas hydrates are not cost-effective, since they use excessive energy, are impractical, or too costly for commercial production. The three main methods are:
Depressurization
Reducing the reservoir pressure below the hydrate equilibrium pressure to free the methane is not commercially viable due to the need to
(a) create and maintain a low-pressure (about 500 psig) production zone to free the methane from the high-pressure (about 2,000 psig) deep-seabed reservoirs of gas hydrates,
(b) continuously remove water equal to the produced methane volume to sustain the low pressure at the production zone, and
(c) have additional surface facilities for dehydrating and compressing the produced methane gas.
Molecular Replacement
This substitution process involves injecting carbon dioxide into a reservoir under the right pressure to extract methane by exchanging methane for CO2 in a gas hydrate crystal. This process is not commercially viable due to the need to deliver large volumes of CO2 under the right pressure to remote deep seabed gas well sites.
Heating
Increasing reservoir temperature above the hydrate equilibrium temperature to dissociate methane from the ice crystals is not commercially viable. That is due to the need to deliver heat to specific points or molecules in a horizontally dispersed gas hydrate reservoir—which could also cause an uncontrolled release of methane to the environment as a harmful greenhouse gas.
None of these methods can produce methane safely and economically from globally abundant deep-sea gas hydrate deposits, despite the snowballing global demand for cheaper and cleaner energy.