Environment Report 2014

Figure 18: Accidental Oil Release Volumes by Source on the UK Continental Shelf from 2011 to 2013

1

Maintenance Operational

Lubricating Oil

Drainage

Bunkering

Pipework Infrastructure

Hydraulic Systems

Other*

2

1%

1%

3

19%

32%

7%

4

4%

33%

5

3%

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*Other includes process upsets and extremely small leaks from other areas of the installations which do not fall into the other categories above

Source: DECC April 2014

According to the PON1 data, a third of the accidental oil releases during 2011 to 2013 were pipework infrastructure-related. Themajority of the volume (60 of the total 65 tonnes) of oil released frompipework infrastructure is attributable to onemechanical failure incident, which was detected early due to inspections that take place twice daily. The worst case release volume for this event was reported, assuming a continuous release between inspections as it was difficult to establish an exact release volume; the actual volume is therefore expected to be significantly lower. Pipework infrastructure releases also encompass small releases due to wear and tear (on pipework connections in particular), collisions by other third parties as well as mechanical failure of subsea pipework infrastructure. Releases through drainage systems also make up 32 per cent of accidental oil releases from 2011 to 2013. The majority of this volume (56 of the total 64 tonnes) is attributable to one drainage issue experienced over a number of years on one installation; this has now been rectified. This incident did not occur in the 2011 to 2013 period alone and so the volume quoted is cumulative over a number of years, which was then reported in 2013. Small releases of oil from a platform via the drainage system may occur when, for safety reasons, the fire systems are tested. This activates the release of large volumes of water which drains to sea. Also, in extreme weather, closed drainage systems can become over-loaded which results in an overflow of oiled water to the open drainage system that is routed to sea. Hydraulic systems resulted in 19 per cent of accidental oil releases (38 tonnes), including the failure of seals and hoses on cranes and on remotely operated vehicles (ROVs). Operational reasons caused seven per cent (13 tonnes) of the accidental oil volume, encompassing releases caused by human error such as knocking over oil cans or accidentally overfilling tanks. Maintenance operations contributed to four per cent (eight tonnes) as extreme weather conditions or losses of containment due to unexpected circumstances during maintenance can cause releases. Every effort is made to ensure that pipework is free fromoil prior to access, however, occasionally, oil becomes trapped in areas of the pipework or there is a small amount of residue remaining resulting in a small accidental release.

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