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Mariner FSU

The Mariner Floating Storage Unit (FSU) is a permanently moored offshore storage vessel serving the Mariner field in the UK Central North Sea. Installed alongside field start-up in 2019, it receives stabilized crude oil from the Mariner PDQ platform and stores it for offloading to shuttle tankers. It has no production or drilling capability.

Operator: Equinor

Status: Operational

Mariner FSU platform photo

Image Source: Equinor. (All rights belong to the original owner.)

Production: Oil

Operations start: 2018

Water depth: 109 m

Country: UK

Block: 9/11a

Type: FSO

Field

The Mariner field is a heavy oil development in the Outer Moray Firth basin, producing from Paleocene sandstone reservoirs. Due to oil properties and distance from shore, storage and shuttle tanker export were selected as the preferred development concept, necessitating a dedicated offshore storage unit.

Facilities

The FSU functions solely as a crude oil storage and export facility. Stabilized oil is transferred from the PDQ platform via a dedicated pipeline and riser system into the vessel's cargo tanks. The FSU is turret-moored to allow weather-vaning and is permanently stationed at the field location. Systems include cargo pumping, inert gas generation, crude heating and circulation, and custody transfer metering for tanker offloading. Offloading is performed via tandem configuration to shuttle tankers. Utilities include power generation, ballast and bilge systems, fire and gas detection, firefighting systems, and marine control systems. The FSU does not process hydrocarbons beyond storage conditioning and does not handle produced water or gas. Design emphasis is on safe long-term station-keeping, storage integrity, and reliable offloading in severe weather conditions.

Mariner FSU layout
Image Source: Equinor. (All rights belong to the original owner.)

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