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DECOMMISSIONING INSIGHT REPORT

2016

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FPSO

Floating, production, storage and offloading vessel – a floating vessel used

by the offshore oil and gas industry for the processing of hydrocarbons,

storage of oil and the offloading of the oil either to a tanker or into a

pipeline.

Hydraulic workover unit

Remedial work carried out in a well using a mast powered by

hydraulic fluid.

Integral rig

Fixed rig installed at the well location, usually self-contained, with steel or

concrete legs anchored to the seafloor.

Intervention

Well servicing operations conducted within a completed wellbore to

restore or improve production or injection.

Jack-up rig

Self-contained combination drilling rig and barge with legs that can be

raised and lowered independently onto the seafloor.

Jumper

A short segment of flexible pipe with a connector half at either end. A

jumper is commonly used to connect flowlines and/or subsea facilities

together.

Lift-installed jackets

These structures weigh less than 10,000 tonnes and are yard fabricated

before being transported horizontally or vertically on a barge to the field.

Once at the field, the jacket is lifted from the barge into position using a

suitable crane vessel.

Making safe

‘Making safe’ of facilities includes cleaning, freeing equipment of

hydrocarbons, disconnection and physical isolation, and waste

management. ‘Making safe’ of pipelines involves depressurising them and

removing any hydrocarbons. Then the pipelines are cleaned and purged,

with the cleaning programme based on the specific needs of the system.

This may involve the use of pigs, which are maintenance tools used to

clean or inspect the insides of pipelines.

Manifold

A manifold in the context of oil and gas production is a pipe to which wells

are connected in order to collect, co-mingle and direct fluid flow from

more than one well. Such an installation can be on a platform or on the

seabed for accumulating several subsea wells. Manifolds can be used for

the distribution of fluids for injection into a series of wells.

Mattresses

Mattresses are often used to provide protection, for stabilisation, and as

crossover support for pipelines. These comprise flexible blocks linked with

rope or wire, or concrete forms or grout bags filled with cement.

MER UK

Maximising Economic Recovery from the UKCS

Milling

A mill or similar downhole tool is used to remove casing in the well where

a barrier needs to be installed in case of pressure or potential movement

of hydrocarbons behind the casing. The objective is to prevent fluids

flowing into another formation or to the surface.

Modular rig

Rig designed in modules that can be lifted onto a platform by crane to be

erected on site.

NNS

Northern North Sea

NUI

Normally Unmanned Installation

OGA

Oil and Gas Authority

Over-trawl surveys

Over-trawl surveys make sure the seabed is safe for normal fishing

activities to resume.

Pig

A device used to clean pipelines.