Perenco – Bringing out of use pipelines back into use

Submitted by Perenco

Impact

The immediate effect of taking the pipeline out of use was the loss of 60,000 barrels of water injection capacity per day on Furzey Island, ultimately leading to a loss of ~2,400 barrels of oil production per day.

The conventional Horizontal directional drilling option would have taken ~ 14 months to complete at a cost of ~ £5M. The deferred production during this period could be estimated to be over 1 million barrels of oil. In addition a new pipeline would require significant consultation and planning permission to drill in an environmentally sensitive area.

The selected ‘Pipe in pipe’ solution was completed in 6 months for a cost of £2.2M and a deferred production of 430 thousand barrels of oil.

Description of Best Practice

The Wytch Farm Oil field is situated in one of the UK’s most environmentally sensitive areas. On 9th March 2015 following a routine in-line inspection, a 1.2km section of 8” produced water pipeline connecting Furzey Island (in Poole Harbour) with F site (on the Goathorn Peninsula) was found to have severe internal corrosion. The pipeline was immediately taken out of service as a precaution to protect the environment and a project was initiated to restore production.

Conventionally the pipeline would have been decommissioned and replaced using a technique called ‘Horizontal directional drilling’. This would involve a significant project drilling a 1.2km borehole between the two remote sites. A new steel pipeline would then be constructed on the mainland and pulled through the new borehole. Finally the new pipeline would then need to be connected by welding into the buried pipelines at each site.

With technical support from Perenco’s head offices the local team looked for innovative solutions that could repair or re-use the existing pipeline. These included:

• A tight fit internal sleeve (pulling a PDFE liner into the pipe);
• A ‘cured in place’ pipeline liner; and
• A composite ‘Pipe in Pipe’ pulled through the existing 8” pipeline.

The selected ‘Pipe in Pipe’ solution involved pulling a 5”, 155 bar rated composite pipe through the existing pipeline using a small wireline unit on the mainland.