Environment Report 2015

ENVIRONMENT REPORT 2015

As shown in Figure 12, 76 per cent of CO 2 emissions were generated from fuel consumed by combustion equipment to provide electrical power and drive compressors for gas export. This activity is essential as offshore installations are not connected to the national grid for power supply. Power is required to run equipment used in production processes, for electricity and heat, as well as compression equipment to enable gas to be transported ashore. emissions. Flaring and venting are necessary offshore for maintenance, well testing and, most crucially, for the safety of offshore workers. Gas venting and flaring are both subject to consent under the Petroleum Act 1998, which aims to conserve gas by avoiding unnecessary wastage during hydrocarbon production. Gas flaring is also a source of CO 2

Figure 12: Offshore Emissions Sources of Carbon Dioxide 30 , Nitrogen Oxides, Carbon Monoxide and Sulphur Dioxide in 2014

Emissions Source Fuel Consumption

CO

NO

SO

CO

2

x

2

76% 24% >1%

97%

93%

62% 38%

Gas Flaring Gas Venting

3%

7%

-

-

-

SO 2 emissions have remained steady since 2000. Last year, small amounts of SO 2

emissions were released mainly

through fuel combustion. In 2013, SO 2

emissions from offshore oil and gas made up less than one per cent of the

total UK SO 2

emissions 31 .

CO emissions have also been declining since 2000. Although NO x are 11 per cent lower than levels in 2000. The variability in NO x emissions could be attributable to changes in the need for diesel usage when reservoir gas supply is unavailable. This can be caused by several factors including: drilling activity, new installations being brought online, maintenance turnarounds, turbine ‘trips ‘or disruption to the gas supply. Last year, 46,000 tonnes of NO x were released offshore. and CO emissions come from combustion equipment such as turbines, engines and heaters, with turbines being the largest contributor. Reducing both NO x and CO from offshore turbines is quite complex and often challenging. This is due to the unique operating conditions experienced offshore. The majority of offshore turbines are run in load share (i.e. two or more turbines share the load) at low loads of less than 70 per cent. If one turbine experiences operating difficulties, the other turbine(s) can pick up the load quickly to ensure that power to the installation is maintained. This is a common operating practice on the UKCS due to the need for reliability in power generation as offshore installations are not connected to the national grid for power supply. This is essential for the safety of offshore workers. The need to maintain this operating procedure, as well as the technical challenges associated with running turbines with variable fuel gas quality, has meant that emissions reduction technologies such as Dry Low NO x burners are not suitable for use in many circumstances offshore 32 . emissions have been variable, 2014 NO x emissions While relatively smaller amounts of CO and NO x can be emitted through flaring, the majority of NO x

30 Fugitive emissions (leaks and other unintended or irregular releases) and emissions from oil loading are also small sources of CO 2 emissions 31 2014 data were not available at the time of writing. The data came from the Department for Environment, Food & Rural Affairs. See http://bit.ly/1MD8QNo 32 Oil & Gas UK’s Technical Note on Offshore Gas Turbines and Dry Low NO x Burners – An Analysis of the Performance Improvements (PI) Limited Database is available to download at http://bit.ly/1MwT4jI

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