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The 2010 production systems and related equipment proportion (73 per cent of the total mass) is notable as it
was dominated by eight releases of more than ten tonnes each. The largest of these was a release of 136 tonnes
of a low hazard production control fluid due to the failure of a seal on a subsea template valve. This is the worst
case release amount and contributes to the relatively large (26 per cent) contribution of seal failure to the causes
of incidents in 2010.
Other notable releases were in 2012 when 364 tonnes of oil-based fluid were released following a wellbore loss of
containment and, in a separate incident, 139 tonnes of water-based fluid were released from a wellbore. In 2013,
there were two large releases from hydraulic systems, one of 54 tonnes of a low hazard hydraulic fluid and one of
189 tonnes of monoethylene glycol, which is designated PLONOR. These masses are the worst case estimations
for each incident and so the actual amount released is likely to be less. The graph also shows clearly the significant
impact on total mass for each year that the individual large events have.
Figure 32: Accidental Chemical Release Mass by Source
0
50
100
150
200
250
300
350
0
100
200
300
400
500
600
700
800
900
1,000
2010
2011
2012
2013
2014
2015
Number of Releases
Accidental Chemical Release Mass (Tonnes)
Hydraulic Systems
Subsea Systems and
Related Equipment
Pipework Infrastructure
Containers
Bulk Transfer Systems
Drainage Systems
Production Systems and
Related Equipment
Other*
Number of Releases
Source: BEIS July 2016
*Other includes releases from flare systems, deck washings, fire fighting and those releases for
which no source is identified. Shading highlights single large spills in that particular category
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2
3
4
5
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