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7.4 Pipeline Decommissioning
The pipeline network in the North Sea is in excess of 45,000 kilometres and is used to deliver hydrocarbons
to receiving facilities and end-users across Europe. This transportation network is of vital importance when
the economics of field-life extension projects and future development opportunities are being assessed and
it is therefore essential that major pipelines are not decommissioned prematurely. The deferral of pipeline
decommissioning to the end of field life, or for possible reuse, is sometimes carried out under the Interim Pipeline
Regime, whereby the regulator may request that the pipeline owner carries out ‘making safe’ activities and
maintains the pipeline for possible future reuse.
Pipelines on the UKCS include rigid pipelines and flexible flowlines. Their diameters can vary between two and
44 inches. Options for decommissioning include full removal, decommissioning
in situ
, trenching and burial. The
approach adopted will be based on comparative assessments of the different options and a number of factors,
including safety, environmental, technical feasibility, other sea users and cost. All decisions are made on a
case-by-case basis in consultation with key stakeholders and with regulatory approval.
7.4.1 Central and Northern North Sea/West of Shetland
The number and length of pipelines to be decommissioned in these regions over the next decade has increased
since the 2014 report by over 1,300 to 2,190 kilometres. Eighty per cent of the rise is because of new projects and
the remainder is due to more detailed activity forecasts for existing projects. The largest increase is in the ‘other
pipelines’ category, which is defined as pipelines with a diameter less than 16 inches and includes tie-backs, short
flowlines and bundles.
The average length of pipeline to be decommissioned over the next decade is less than four kilometres and it is
deemed that no major transport lines are forecast to be decommissioned in these regions.
Pipeline decommissioning is closely aligned to pipeline ‘making safe’ (see section 7.2), as these activities are
typically carried out sequentially (see Figure 24 overleaf). Activity is forecast to increase year-on-year from 2017
to 2019 and will peak in 2021. Oil & Gas UK expects that activity will smooth out as forecasts are revisited.
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