Page 102 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

the reproductive cycle and health of wildlife in the vicinity of oil and gas
installations.

The major short-term environmental impact is from spills associated with
accidents. These spills can have dramatic short-term effects on the local
environment, with damage to marine- and wildlife. However, the effects
seldom last for more than a few years outside Arctic regions.

7.2.2 Greenhouse emissions
The most effective greenhouse gas is water vapor. Water naturally
evaporates from the sea and spreads out and can amplify or suppress the
other effects because of its reflective and absorbing capability.

The two most potent emitted greenhouse gases emitted are CO 2 and
methane. Because of its heat-trapping properties and lifespan in the
atmosphere, methane's effect on global warming is 22-25 times higher than
CO 2 per kilo released to atmosphere. By order of importance to greenhouse
effects, CO 2 emissions contributes 72-77%, methane 14-18%, nitrous oxides
8-9% and other gases less than 1%. (Sources: Wikipedia, UNEP)

The main source of carbon dioxide emissions is burning of hydrocarbons.
Out of 29 Billion Tons (many publications use Teragram Tg = Million tons) of
CO 2 emitted in 2008, 18 Billion Tons or about 60% of the total comes from oil
and gas, the remainder is coal, peat and renewable bioenergy such as
firewood. 11% or 3,2 Billion tons comes from the oil and gas industry itself in
the form of losses, local heating, power generation etc.

The annual emissions amount to about 1% of total atmospheric CO 2, which

is in balance with about 50 times more carbondioxide dissolved in seawater.
This balance is dependent on sea temperature: Ocean CO 2 storage is
reduced as temperature increases, but increases with the partial pressure of
CO 2 in the atmosphere. Short term the net effect is that about half the CO 2
emitted to air contributes to an increase of atmospheric CO 2 by about 1,5
ppm annally.

For methane, the largest source of human activity-related methane
emissions to atmosphere, is from rice paddies and enteric fermentation in
ruminant animals (dung and compost) from 1.4 billion cows and buffaloes.
These emissions are estimated at 78.5 Tg/year (source: FAO) out of a total
of 200 Tg, which is equivalent to about 5,000 Tg of CO 2. Methane from the
oil and gas industry accounts for around 30% of emissions, mainly from
losses in transmission and distribution pipelines and systems for natural gas.

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