Marine hydrocarbon discharges and spills

The total amount of hydrocarbons discharged decreased by over 300 tonnes between 2004 and 2005.

Figure 4: UKCS Total Discharge of Hydrocarbons, all sources, 2001-2005

During 2005, the 71 installations discharging oil-in-produced-water reported a total of 240 million tonnes of water containing 4,908 tonnes of oil being discharged to sea. The average 2005 concentration of oil-in-produced-water for all installations was 20.5 parts per million (ppm), significantly below the current OSPAR requirement of 40ppm and the industry voluntary target of 30ppm.

Evidence suggests that oil-in-produced-water has no significant impact on the marine environment and recent surveys indicate that the concentration of hydrocarbons in seabed sediments is declining rapidly. In spite of this, UK industry is working collaboratively to achieve the OSPAR requirement to discharge 15% less oil-in-produced-water compared to 2000 levels, through a combination of engineering projects tied into a Produced Water Permit Trading Scheme.

Figure 5: UKCS Average Oil Content of Discharged Produced Water 2001-2005

The tonnage of oil reaching the marine environment as a result of spillages remains relatively constant year on year. In 2005, 77.5 tonnes of oil were accidentally released as a result of 437 incidents. Of these spills, 97% were 1 tonne or under, with only one significant spill of 17.4 tonnes. Crude oil accounts for 48% of total oil released.

Figure 6: Tonnes of UKCS Oil Spilled 2001-2005

Marine chemical discharges

Although discharges of Production, Pipeline and Drilling chemicals have all increased since 2004, levels are still below those in 1999; overall chemical usage is down by 15% to 396,217 tonnes, and chemical discharge is down by 26% to 134,280 in 2005. OCNS Highest Risk Category are less than 5% of 1999 levels, indicating that the majority of chemicals discharged pose low risk to the marine environment.

Figure 7: UKCS Chemicals Discharged by Type 2001-2005