Environment Report 2014

ENVIRONMENT REPORT 2014

Hydraulic systems accounted for 42 per cent (308 tonnes) of accidental chemical releases over the period 2011 to 2013. This includes subsea systems as well as pipework that carry hydraulic fluids to these systems.

Some subsea hydraulic systems offshore are open systems. Open hydraulic systems are designed so that fluid is supplied to valve actuators. Actuating the control valves releases the fluid to the marine environment. By the very nature of their design, releases from these systems are unavoidable. The current legislative regime requires operators to report these releases as accidental PON1s. It is argued that it would be appropriate to consider seeking a permit for these releases, categorising them as planned discharges. The hydraulic systems category also comprises accidental releases from wear and tear on pipework carrying hydraulic fluid to conductor tensioners and blowout preventers (BOPs) for example. Repair of this pipework is complex and may involve mobilising vessels to replace the line completely which can have long lead times. The hydraulic fluids used offshore are mostly water-based and there is no significant environmental impact associated with their release. Pipework infrastructure releases represent 23 per cent (173 tonnes) of accidental chemical releases over the period 2011 to 2013. This is due to corrosion on subsea pipework and seal failures on pipework connections carrying chemicals to injection systems and produced water systems. Operational releases due to human error account for 23 per cent (173 tonnes) of chemical releases during the 2011 to 2013 period. This category encompasses incorrect operation of valves, incorrect routing of injection systems and overfilling of tanks. A small proportion of chemical releases stem from drilling operations (six per cent) and bulk transfer (four per cent) due to hose line damage.

Figure 23: Accidental Chemical Release Volumes by Source on the UK Continental Shelf from 2011 to 2013*

Process Upsets

Drilling Related

Bulk Transfer

Pipework Infrastructure

Operational

Hydraulic Systems

2%

6%

4%

42%

23%

23%

*Please note: Of the chemical releases from 2011 to 2013, 0.23 per cent stem from unknown sources. All percentages displayed in this graph have been rounded accordingly.

Source: DECC April 2014

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