Using CO2 to Unlock Gas Hydrates

What is a gas hydrate?  Gas hydrates are crystalline solids consisting of gas molecules (primarily methane) that form in very low temperature, very high pressure environments.  Each one of these molecules is surrounded by a tight cage of water molecules.  Said more eloquently, “Water molecules fuse with the gas, forming tiny crystals that resemble white or rainbow-colored sorbet, nestling in sediment on ocean floors, in deep lake beds and beneath the Arctic.”1  USGS geologists believe that there are over 21,000 TCF of methane hydrates just in the Gulf of Mexico.  According to the Energy Information Association (EIA), demand for natural gas in the US will increase from 22 TCF a year to 26 TCF a year by 2030.  The challenge lies in finding a technology to “crack the code to large-scale extraction of these energy rich substances”.2

The National Energy Technology Lab (NETL,) in coordination with the US Department of Energy (DOE,) has chosen ConocoPhillips “to perform the first field trial of a promising technology that would allow the production of methane from gas hydrates on Alaska’s North Slope”.3  This is part of their National Methane Hydrates R&D Program, which is internationally known for their research in methane hydrates.  ConocoPhillips was selected for this project because of the patented technology they developed along with the University of Bergen (Norway).  The technology allows for methane hydrate production “whereby carbon dioxide molecules are exchanged in situ for the methane molecules within a methane hydrate structure, releasing the methane for production.”4  So, not only could methane hydrates provide access domestically to the cleanest burning fossil fuel, but this technology could also help with carbon emissions as the CO2 is sequestered during the exchange.  ConocoPhillips has had great success with the technology in lab tests, but this trial will be the first attempt at using the technology in a real world setting.

Diagram of how the technology works:

 

The trial is a three phase project to be completed over 27 months.  Phase 1 has been completed and phase 2 should be completed by the end of this year.  These two phases included the evaluation of field sites and a selection of the top five.  Once the fields have been selected, they will proceed by acquiring approval for approval for access to recommended field test sites through the balloting process.

ConocoPhillips Field Test Site:

 

A more technical description from the NETL website: Key observations in those studies include the rapid rates of carbon dioxide – methane exchange in hydrates formed in porous media under a range of initial conditions, the efficiency of the carbon dioxide displacing the methane from the hydrate structure that approaches theoretical limits, and the preservation of measurable permeability in the porous media during hydrate formation and exchange. The most important observation is that the exchange process does not involve the release of free water to the pore system. Instead, the process appears to dissociate and reform hydrate at very fast rates and on a micro-scale in such a manner that there is no free water formed or significant heat-of-reaction issues.5

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