16 January 2012

Massive Unconventional Hydrocarbon Resource Rising in Importance

Methane hydrate, as the substance is known, has long been regarded by oil and gas companies as a nuisance because it can block marine drilling rigs.

Now a study by Statoil, Norway's state oil firm and a leading global gas producer, suggests it should be reclassified as a major fuel resource, with enough buried in the oceans to power the world for decades or even centuries.

"The energy content of methane occurring in hydrate form is immense, possibly exceeding the combined energy content of all other known fossil fuels," said Espen Andersen, Statoil's exploration manager in unconventional hydrocarbons, who will present his study at an energy conference next week. _Australian_via_SundayTimes
Der Spiegel

Methane, trapped in an icy cage of water molecules, occurs in permafrost and, in even greater quantities, beneath the ocean floor. It forms only under specific pressure and temperature conditions. These conditions are especially prevalent in the ocean along the continental shelves, as well as in the deeper waters of semi-enclosed seas (see graphic).

World reserves of the frozen gas are enormous. Geologists estimate that significantly more hydrocarbons are bound in the form of methane hydrate than in all known reserves of coal, natural gas and oil combined. "There is simply so much of it that it cannot be ignored," says leading expert Gerhard Bohrman of the Research Center for Ocean Margins... _DerSpiegel
Researchers around the world are scrambling to find economical ways of recovering this vast hydrocarbon resource.
One intriguing idea for the simultaneous recovery of energy and sequestration of global warming gas is proposed by the transformation of methane hydrates to carbon dioxide hydrates with the injection of liquid CO2. Here we use molecular dynamics simulations to show that the replacement can take place without melting of the network of hydrogen-bonded water molecules. Depending on the distance to the interface between the liquid CO2 and solid clathrate hydrate, we find that the replacement occurs either via direct swapping of methane and CO2 or via a transient co-occupation of both methane and CO2 in one cavity. Our results suggest that, with a careful design of the operation condition, it is possible to replace methane from methane hydrates with CO2 in the solid phase without much change in the geological stability. _ACS Abstract


A team of American and Japanese researchers are in Alaska this month to test a new method of extracting methane hydrates from rich Arctic resources. They intend to inject CO2 into the hydrates in hopes that the waste gas will replace the more valuable methane in the ice cage, freeing up the methane for extraction and use.
This month, scientists will test a new way to extract methane from beneath the frozen soil of Alaska: they will use waste carbon dioxide from conventional wells to force out the desired natural gas.

...The test will use the Ignik Sikumi well, which was drilled on an ice platform in Prudhoe Bay last winter. Specialized equipment has been installed, including fibre-optic cables to measure the temperature down the well, and injection pipes for the CO2. “None of this is standard equipment; it had to be built to design,” says Boswell.

...During the test, the researchers will inject nitrogen gas into the hydrate deposit to try to push away any free water in the system, which would otherwise freeze into hydrates on exposure to CO2 and block up the well. The next phase is to pump in isotopically labelled CO2, and let it ‘soak’ for a week before seeing what comes back up. This will help to test whether the injected carbon is really swapping places with the carbon in the hydrates. Finally, the team will depressurize the well and attempt to suck up all the methane and carbon dioxide. This will also give them a chance to test extraction using depressurization — sucking liquids out of the hydrate deposits to reduce pressure in the well and coax the methane out of the water crystals. “We’ll continue to depressurize until we run out of time or money, and see how much methane we can get out that way,” says Boswell. _Nature

As humans devise more and better ways to utilise methane in place of crude oil, it makes sense to learn how to extract the richest reserves of methane in the crust.

We do not yet know how much of the methane resource originates abiotically in the mantle -- and thus can be theoretically seen as "renewable methane." It is likely to be substantial. And thanks to the giant tectonic plate mechanism, with ongoing subduction of organics-rich oceanic crusts under continental crusts, biogenic methane is, to a large extent, renewable as well -- on an extended time scale, and on a continuous basis. Where do you think most of these methane hydrates came from in the first place? No matter. There are a lot more where those came from.

Adapted from an article published on Al Fin Energy

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