Subsea Pipeline Unblocked On-Line

Outfall pipeline between offshore installation and land depot

Summary

The 4km x 16” subsea pipeline between a small North Sea offshore installation and its land based storage depot had become blocked with wax and a stuck pig causing major disruption for the operator. Tube Tech’s successfully removed the blockages using only two access points.

Challenge

• 4km subsea pipeline – half located underwater and half on land
• Pipeline horizontal with slight gradient of 22.5 degrees then 22.5 degree levelling out horizontal.
• Pig used by previous contractor had become stuck in the pipe as the tracer had failed.
• Unknown volume of wax behind or in front of pig along entire length of 16 inch I.D.pipeline
• Two access locations used to avoid using divers due to a 12 knot rip tide.

Solution

• Tube Tech ‘hot tapped’ into a pressurised system and removed pig by a bespoke “drilling” method.
• Once pig removed the remainder of the line was cleaned to production standard using a variety of cleaning heads to suit heavy scale and other fouling characteristics.
• Highly qualified offshore trained personnel mobilised within 2 weeks for this critical world first project.
• The pipeline was inspected before, during and after the cleaning process.
• Actual cleaning time was 1 week

Tube Tech comment

Mike Watson, Technical Director:  “Most definitely one of our biggest challenges to date. The Client’s only alternative was the use of ships shuttling back and forwards or laying a new pipeline. Substantial 6 figure sums per day where being lost while the sub sea pipeline was out of action. Being able to respond so quickly and with the appropriate pipeline cleaning techniques meant we were able to solve what appeared to be an ‘impossible challenge.”