Environmental Report 1999 Index

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Atmospheric Emmissions During oil and gas exploration and production activities, volumes of waste gases are inevitably produced. The main sources of gaseous emissions are: exhaust gases produced by combustion of fuel gas or diesel for power generation; exhaust gases produced by the gas turbine-powered compressors used to export gas to onshore terminals and the consumer; flaring or venting of hydrocarbon gas. The quantities of waste gases produced in 1998 by UKOOA members are shown in Figure 12. The environmental significance of each of these waste gases is explained later. These figures have been calculated using data on the quantities of fuel gas and diesel fuel burned by each UKOOA member, as well as the quantities of gas flared or vented under consents issued by the DTI. Figure 11 Gas Offshore production platforms Offshore mobile drilling rigs Onshore E&P facilities   Tonnes Tonnes Tonnes Carbon dioxide 19,429,352 1,462,841 3,878,272 Carbon monoxide 31,645 7,752 3,984 Nitrogen dioxide 48,164 18,575 7,202 Sulphur dioxide 4,068 7,575 555 Methane 64,134 7,380 15,637 Volatile hydrocarbons 76,522 3,536 104,416 Figure 12 summarises the total emissions from 1996 to 1998. Figure 12 Year Carbon dioxide Carbon monoxide Nitrous oxide Sulphur dioxide Methane VOCs 1996 23,608,392 43,791 63,525 10,581 98,034 175,391 1997 23,122,018 41,519 65,241 14,234 92,462 182,451 1998 24,770,465 43,381 73,941 12,198 87,151 184,474 The major source of atmospheric emissions is fuel gas, which accounts for almost 60% of CO2 emissions (see Figure 13). Figure 13 Source Percentage fuel gas 59.53% flare gas 26.07% Diesel 9.80% Venting 0.02% well testing 3.26% Other 1.33% Gas Flaring Natural gas is a valuable commodity that UKOOA members produce and sell to industry, consumers and other gas distributors. Not surprisingly, they try not to waste any by letting it escape to the atmosphere. Nevertheless on most platforms, small amounts of gas are deliberately burnt in the flare system. Flaring, which accounts for about a quarter of the industry's atmospheric emissions, takes place for two reasons. On installations that produce both gas and oil (most fields produce at least some 'associated gas', as it is called), a flare is kept lit at all times as a vital safety precaution. The flare acts as a pilot light so that, if necessary, large volumes of gas can be diverted to the flare, where they are immediately ignited and safely burnt off. This may happen for operational reasons, during maintenance procedures, or during startups and shutdowns. On installations that export associated gas to shore, the amount flared is kept to the minimum required to keep the flare alight. However, some fields do not produce gas in quantities that would justify the investment needed to transport the gas to shore. In these cases, gas may be re-injected into the reservoir to help maintain reservoir pressure whilst some will be flared to maintain oil production rates. Gas flaring is controlled by the DTI through a 'Flare Consent' which puts a ceiling on the amount of gas each facility can flare each year. Because gas has economic or practical value, operators reduce the amount flared even further, if possible. Figure 14 Year Gas flared (tonnes)   Onshore Offshore Total 1996 253,686 2,054,542 2,308,228 1997 182,586 1,860,947 2,043,533 1998 169,177 1,886,572 2,055,749 Environmental Impacts Of Atmospheric Emissions Carbon dioxide, methane and, to a lesser extent, nitrous oxide are all greenhouse gases that are thought to contribute to climate change. We acknowledge the subsequent use of oil, condensate and gas as energy products results in emissions of CO2 . This is being addressed as part of the UK's commitment under the Kyoto Protocol. As mentioned earlier, end use issues are beyond the scope of this report which focuses on emissions from offshore exploration and production operations (please see the end of this report for other useful addresses). In the past three years, UKOOA member's CO2 emissions have increased slightly (by 5%), methane emissions have decreased by more than 10%, and NOx emissions have increased by 14%. NOx, SOx and VOCs contribute to regional effects such as acid rain and ground level ozone. Although NOx is linked to health issues because it is involved in the formation of photochemical smog, the health effects of NOx are generally localised, and the impact from offshore oil and gas installations is not significant when compared with onshore sites. NOx is also the largest contributor to acid rains, which may damage vegetation and aquatic species. However, the evidence gathered in several studies suggests that offshore emissions in the North Sea are not a major source of acid deposition. Figure 15 shows UKOOA members' gas emissions for 1996 as a percentage of the total emissions in the UK in 1996, the latest year for which DETR data is available (DETR Digest of Environmental Statistics No 20, 1998). Unfortunately there are no figures for the total UK emissions for 1998 yet and it is therefore not possible to compare UKOOA figures for that year. Figure 15   UK Total emissions 1996 Tonnes UKOOA percentage 1996 % CO2 593,000,000 4.0 Methane 3,710,000 2.6 NOx 2,060,000 3.1 SOx 2,028,000 0.5 VOC’s 2,111,000 8.3