| Precision Combustion, Inc. (PCI)
is developing a downhole catalytic combustor for efficient production of
methane from its hydrate.
Gas
hydrate is a crystalline solid (see photo at right) consisting of
gas molecules, each surrounded by a cage of water molecules. The gas is
held in this state by a combination of low temperature and high
pressure. If the gas could be effectively, safely and controllably
tapped, gas hydrates offer the potential for making major contributions
to meeting DOE primary objectives regarding energy needs and energy
independence while substantially expanding available world energy
reserves.
Methane hydrate deposits are abundant throughout the
world and have been estimated to represent the greater portion of the
world’s fossil energy reserves. Estimates of hydrate natural
gas on the North Slope of Alaska beneath existing
facilities are in the 10’s of trillions of cubic feet, with additional 100’s of trillions
of cubic feet in
areas that do not yet have infrastructure. The estimates for
hydrate natural gas beneath the U.S. continental margin is even larger, on
the order of 1,000’s of trillions of cubic feet (Sloan, et. al, 2008). "The U.S. Geological
Survey estimates that methane hydrate may contain more organic carbon than
all the world's coal, oil, and non-hydrate natural gas combined. The
magnitude of this previously unknown global storehouse has raised serious
inquiry into the possibility of using methane hydrate as a source of
energy." [U.S. DOE Methane Hydrate Program].
"Even a deposit as thin as
fifty feet in height contains an intriguingly large amount of gas. Such a
single six square mile deposit in the arctic or Gulf of Mexico or off the
Oregon coast with hydrate in only 50% of the pore volume would contain over
200 billion cubic feet of natural gas worth $400Mil at $2/Mscf. Thus,
extraction of methane from hydrates could provide an enormous energy and
petroleum feedstock resource. Additionally, conventional gas resources
appear to be trapped beneath methane hydrate layers in ocean sediments."
[U.S. Geological Service] PCI is developing an application under a U.S.
Department of Energy Small Business Innovation Research contract
that is based on in-situ generation
of heat rather than transporting a heated fluid. Combustion downhole
avoids wellbore heat losses and air pollution, and, in the arctic,
damage to the permafrost.
Catalytic combustion has proved to be an efficient technique for the clean
combustion of fuels, including humid methane released from the gas hydrates
and had been demonstrated to be suited for a downhole combustion system. This
application offers the potential for an economic technology for
substantially increasing world available energy reserves and may provide a
global warming benefit through CO2 sequestration. CO2 hydrate is
thermodynamically more stable than methane hydrate, it will exist at a
higher temperature than methane hydrate, and the CO2 hydrate heat of
formation (exothermic) is slightly greater than the heat of dissociation
(endothermic) for methane hydrate. This means the possibility exists for
economic sequestration of CO2 into the methane hydrate bed, advantageously
stabilizing the bed, and further reducing required heat from combustion. |
Methane hydrate crystals
1000s of trillions of cubic feet of methane
lie beneath protected areas of the US. The
challenge is extracting it without disturbing
the landscape.
Depiction of the downhole heat generator
(click to view larger) |
