Environment Report 2013

ENVIRONMENT REPORT 2013

6.3 Oil Discharges Up to 2006, oil concentration in produced water was measured using the infrared method (IR). The IR method measures both the dispersed and dissolved hydrocarbons extracted with solvent. The method can, however, include other organic chemicals, giving an artificially high result and can also underestimate dissolved hydrocarbons. To rectify this and to provide a more accurate analysis of hydrocarbon content, OSPAR agreed (Agreement 2005-15) the use of a new method for oil-in-water analyses, based upon a modified version of the ISO 9377-2 (GC-FID) method. The difference in reported discharges due to the change in analysis method makes comparison of recent data with previous years difficult. For most fields, however, the concentration of oil-in-produced water has reduced over time through investment in separation technologies as well as re-injection projects. Measured using the GC-FID method, the discharged oil quantities to sea in 2012 were 2,267 tonnes based on an average concentration of 14.6 milligrammes per litre. This is comparable with values since 2007.

Figure 5: Oil-in-Produced Water Discharges from 2000 to 2012

Oil Discharged with Produced Water Average Oil Content with GC-FID Method

Average Oil Content with IR Method

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000

25

20

15

10

Tonnes

5

Milligrammes per Litre

0

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Source: EEMS August 2013

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