South Sean

Location and Geology

• The South Sean gas field is located in the Southern North Sea (SNS) gas province on the UK continental shelf (UKCS), specifically in blocks 49/25a, 49/30a, and 49/24e.
• It is situated in shallow water, with a water depth of approximately 30 meters (or 230 feet).

Ownership and Operation

• The field is operated by One-Dyas UK, a subsidiary of the Dutch exploration and production company One-Dyas.
• The ownership is shared between One-Dyas and Viaro Energy.

Production History and Status

• The South Sean gas field has been in production since 1986, as part of the larger Sean gas field development.
• The field has recovered 72.76% of its total recoverable reserves as of the last available data. Peak production was achieved in 2019.
• Based on economic assumptions, production from the South Sean field is expected to continue until the field reaches its economic limit in 2038.

Infrastructure

• The Sean gas field, which includes South Sean, comprises three separate fields: East Sean, North Sean, and South Sean.
• The field is developed with three platforms: a wellhead and compression platform (Sean PD), a production and accommodation platform (Sean PP), and a not permanently attended installation (NPAI) called Sean Romeo (Sean RD).
• The platforms are interconnected; Sean RD and Sean PP are connected through a 20-inch diameter gas export pipeline (PL310), and there is an electrical cable between Sean PP and Sean RD.

Decommissioning Plans

• Although the specific decommissioning plans for the South Sean field are not detailed separately, the broader Sean gas field decommissioning program provides some insights.
  • The decommissioning of the Sean gas field, including its associated infrastructure, is scheduled to be completed by 2029. This involves the removal of the three fixed steel platforms, associated subsea infrastructure, and related pipelines.
  • The topsides and substructures of the platforms will be completely removed and transported onshore for dismantling, recycling, or disposal. The substructure piles will be cut 3 meters below the seabed before removal.
  • Wells will be plugged and abandoned in compliance with guidelines issued by Oil & Gas UK.

Pipeline and Export

• The gas produced from the Sean field, including South Sean, is transported to Shell UK’s Bacton Terminal in North Norfolk, UK, via a 106.5 km long and 30-inch diameter gas export pipeline named PL311.

Other Relevant Details

• The field's infrastructure includes several pipelines, umbilical crossings, and mattresses placed over the pipelines. These will be flushed and filled with inhibited seawater before decommissioning to ensure they are fit for future re-use.
• The decommissioning process also involves the removal of mooring buoys, electrical cables, and other associated infrastructure.

In summary, the South Sean gas field is an integral part of the larger Sean gas field complex, operated by One-Dyas UK, with production expected to continue until 2038. The decommissioning plans, while not specifically detailed for South Sean, are part of the broader decommissioning program for the entire Sean gas field.