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Corrib Field and Subsea Technology
The Corrib field is located approximately 83 kilometres off the coast of County Mayo, in 350 metres of water. The distance from the seabed to the Corrib reservoir is a further 3,000 metres.
Five wells have been drilled at the Corrib field and are ready for production. To drill a well more than 3000 metres below the sea bed, the semi-submersible rig drills section-by-section until it reaches the reservoir. When each section is complete, steel casing is installed and held in place with cement. This makes the well strong enough to withstand the pressure from the reservoir.
Each well will have a “christmas tree” on top of it. This is a structure that contains all the necessary equipment to control, monitor and shut off a well (similar to a tap). The “christmas trees” will be covered by a well protection structure to prevent snagging on fishing nets and to protect them from damage from any dropped objects.
The gas from each of the five wells is piped through individual sections of flexible flowlines to the production manifold where it is combined and co-mingled before being fed into the main pipeline for transport to shore.
The bundle of cables and small diameter tubes called the “umbilical” will carry electrical and hydraulic power to operate the sub sea controls. As the name suggests, this is the lifeline to the sub sea facilities and connects them to the onshore terminal. To protect the gas pipeline, the umbilical will also transport an anti corrosion chemical and methanol (a type of “anti-freeze”) to the wellheads to mix with the gas and prevent “hydrates” (ice-like crystals) from forming in the pipeline.
During the operation phase, the sub sea facilities will be monitored and controlled 24 hours a day from the control room in the onshore gas terminal.