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Extraction loss is collected only on an annual basis. Monthly extraction loss
is estimated from monthly marketed production by assuming that the preceding
annual percentage remains constant for the next twelve months.
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Dry gas production is equal to marketed production (wet) minus extraction loss.
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Supplemental gaseous fuels data are collected only on an annual
basis except for the Dakota Gasification Co. coal gasification facility
which provides data each month. The ratio of annual supplemental fuels
(excluding Dakota Gasification Co.) to the sum of dry gas production,
net imports and net withdrawals from storage is calculated. This ratio
is applied to the monthly sum of these three elements. The Dakota
Gasification Co. monthly value is added to the result to produce the
monthly supplemental fuels estimate.
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Total consumption consists of pipeline fuel use, lease and plant fuel use,
and deliveries to end-use consuming sectors.
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Totals may not equal sum of components because of independent rounding.
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| Storage |
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Net storage withdrawals data through 2006 include underground storage and liquefied natural gas storage.
Data for January 2007 forward include underground storage only.
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All monthly data concerning underground storage are published from the Form EIA-191M, "Monthly Underground Gas Storage Report."
A new Form EIA-191 became effective in January 1994. Injection and withdrawal data are from the Form EIA-191M
survey.
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The final monthly and annual storage and withdrawal data include both
underground and liquefied natural gas (LNG) storage. Annual data on LNG additions and
withdrawals are taken from Form EIA-191M.
Monthly data are estimated by computing the ratio of each month's underground storage
additions and withdrawals to annual underground storage additions and withdrawals and
applying it to annual LNG data.
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There are three principal types of underground storage facilities in operation in the
United States today: salt caverns (caverns hollowed out in salt "bed" or "dome" formations),
depleted fields (depleted reservoirs in oil and/or gas fields), and aquifer reservoirs
(water-only reservoirs conditioned to hold natural gas). A storage facility's daily
deliverability or withdrawal capability is the amount of gas that can be withdrawn from
it in a 24-hour period. Salt cavern storage facilities generally have high deliverability
because all of the working gas in a given facility can be withdrawn in a relatively short
period of time. (A typical salt cavern cycle is 10 days to deplete working gas, and 20
days to refill working gas.) By contrast, depleted field and aquifer reservoirs are
designed and operated to withdraw all working gas over the course of an entire heating
season (about 150 days). Further, while both traditional and salt cavern facilities can
be switched from withdrawal to injection operations during the heating season, this is
usually more quickly and easily done in salt cavern facilities, reflecting their greater
operational flexibility.
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| Imports and Exports |
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Beginning with data for January 2001, EIA is reducing the reported volume of gas imported
by pipeline from Canada by the amount of natural gas liquids removed from the saturated natural
gas carried by Alliance Pipeline. Alliance moves saturated natural gas from the Canadian
border at Sherwood, ND to a processing plant in Illinois. After the adjustment, volumes
of imported natural gas on this pipeline are on the same physical basis as other reported
volumes of pipeline imports.
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Prices for LNG imports are reported as “landed,” received at the
terminal, or “tailgate,” after regasification at the terminal. Generally
the reporting of LNG import prices varies by point of entry, and the
average prices are calculated from a combination of both types of prices.
The price of LNG exports to Japan is the “landed” price, defined as received
at the terminal in Japan.
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Annual and final monthly data are published from the Office of Fossil Energy,
U.S. Department of Energy, Natural Gas Imports and Exports.
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Preliminary monthly import data are based on data from the National Energy Board of
Canada. Preliminary data are revised after the publication of "Natural Gas Annual"
for the calendar year.
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Preliminary monthly export data are based on historical data from the Office of Fossil
Energy, U.S. Department of Energy, Natural Gas Imports and Exports.
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Totals may not equal sum of components due to independent rounding.
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