Oil and gas production handbook An introduction to oil and gas production

Intergovernmental Panel on Climate Change (often called the UN Climate 
Panel) predicts that these emissions will cause the global temperature to rise 
from between 1.4 to 6.4 ºC by the end of the 21
st
 century, depending on 
models and global scenarios.  

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136 
 
9.2.1 Indigenous emissions 
Emissions from the industry can be divided into several types.  
 
Discharge: 
 
Mud, shale, silt, produced water with traces of 
hydrocarbons. Ballast water, polluted wastewater with 
detergent, sewage, etc. 
Accidental spills:  
Blowout, shipwreck cargo and bunker oil, pipeline 
leakage, other chemicals, traces of low level 
radioactive isotopes. 
Emissions:  
CO
2
, methane, nitrous oxides (NO
x
) and sulfur from 
power plants and flaring 
Exposure: 
Toxic and/or carcinogenic chemicals 
Locally, these emissions are tightly controlled in most countries by national 
and international regulations, and during normal operations, emission targets 
can be reached with the systems and equipment described earlier in this 
document. However, there is continuing concern and research into the 
environmental impact of trace levels of hydrocarbons and other chemicals on 
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. 
9.2.2 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 contribute 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 

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137 
 
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 are about 1% of total atmospheric CO
2
, which is in 
balance with about 50 times
 
more carbon dioxide 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 annually. 
 
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 buffalos. 
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.