Decommissioning Insight 2017


Self-contained combination drilling rig and barge with legs that can be raised and lowered independently onto the seafloor. 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. These structures weigh less than 10,000 tonnes and are yard-fabricated before being transported on a barge to the field. Once at the field, the jacket is lifted from the barge into position using a suitable crane vessel. To continuously measure formation properties with electrically powered instruments to make decisions about drilling and production operations. ‘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. 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 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. 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. Rig designed in modules that can be lifted onto a platform by crane to be erected on site. Maximising Economic Recovery from the UKCS

Jack-up rig


Lift-installed jackets


Making safe





Modular rig

Northern North Sea


The Netherlands Oil and Gas Exploration and Production Association


Normally Unmanned Installation


Oil and Gas Authority


Over-trawl surveys make sure the seabed is safe for normal fishing activities to resume. Reverse installation whereby the topsides modules are lifted separately onto a transportation barge or the deck of the crane vessel before being taken onshore. The piece-small method involves dismantling the topside and using onshore demolition techniques to produce small, manageable pieces that can be transported onshore.

Over-trawl surveys




A device used to clean pipelines.

A solid or gel made out of a variety of materials designed to stop up a hole or aperture, to fill a gap, or to act as a wedge.



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