Corrosion protection of offshore steel pipes by retrofitting

Corrosion protection of off-shore steel pipes by retrofitting feltepoxy liners, a method qualification of Insituform™ 1 - Classification: Internal 2010 -11 -19

Background • Since start-up in 1986 less oil, more gas and more water are being produced at Gullfaks • Less demand for oil storage capacity • Re-assign oil storage tanks to produced water settling tanks 2 Classification: Internal 2010 -11 -19

Challenges • Carbon steel piping from utility shaft to storage cells − Crude oil OK − Produced water corrosive • Piping cannot be replaced • Corrosion protection essential • One-sided access only • Long and intricate routing of pipes • Pipe failure or blockage → loss of storage cell 3 Classification: Internal 2010 -11 -19

Considerations • Internal painting ruled out − Surface preparation extremely difficult − Paint application − Inspection • Cathodic protection ruled out − Temperature, Oxygen, Chlorides and Sulfides − Uncharted territory • Liner most favoured solution 4 Classification: Internal 2010 -11 -19

Liner Requirements • Loose liner ruled out → rigid liner • Compliant during placement → thermoset based • Adhesion to pipe surface cannot be critical → structural liner • Be able to ensure position of liner end → non-stretch liner • Ample ‘pot-life’ → epoxy • ‘What if’ contingencies → ensure back-up solutions for relevant failures during installation 5 Classification: Internal 2010 -11 -19

Insituform™ from Olimb AS • Thermoset liner based on felt and epoxy • Felt thickness can be tailored to give appropriate structural capacity • Epoxy quality can be chosen to give temperature and chemical performance (NA) • Inserted (inverted) into pipe using compressed air • Cured using steam • Mature product in terms of renovating municipal piping • Less history on complex geometries • Ensure most demanding relining is well within the process window → do a test relining of replica of most challenging pipe on land 6 Classification: Internal 2010 -11 -19

Pipe replica • Length of chosen pipe approx 80 metres • Pipe diameter 16’’ • Starts off with 3 x 90º bends then 12 m straight up • Then 10 more bends 7 Classification: Internal 2010 -11 -19

In a quarry near Moss 8 Classification: Internal 2010 -11 -19

The liner principles • A tubular felt sheath clad with a layer of PU on the outside • Prior to placing the liner in the pipe, the felt is saturated with epoxy • Even distribution of epoxy using rollers • Curing can be delayed by placing in cold water 9 Classification: Internal 2010 -11 -19

The liner principles • Silicone ‘plug’ loosely glued to end of liner • Perforated to allow controlled escape of steam • Glue must allow pull-off by attached rope after curing 10 Classification: Internal 2010 -11 -19

Liner reeled • Lubricant applied to outer surface • Rope and liner reeled up inside pressure vessel 11 Classification: Internal 2010 -11 -19

Inverting the liner • Rope and liner reeled up inside pressure vessel • End of liner pulled back over spout • Tank pressurised to force liner into pipe 12 Classification: Internal 2010 -11 -19

A sketchy illustration. . . → o → Pressure vessel 13 Classification: Internal 2010 -11 -19 Liner Corroded pipe

Results • Maximum recorded pressure 1. 2 barg − Allowable 1. 5 barg − Burst 2. 5 barg • All bends negotiated first attempt • Curing temperature achieved at far end • Silicone ‘plug’ came off (no force measurements were done) • End of liner within tolerances • No contingency plans were put into action 14 Classification: Internal 2010 -11 -19

Results • Destructive inspection of pipe revealed • Wrinkles at the bends • Some lack of adhesion to the steel • Minor liner thickness variations • The method is deemed successfully qualified for this application 15 Classification: Internal 2010 -11 -19

Thank you Corrosion protection of off-shore steel pipes by retrofitting felt-epoxy liners, a method qualification of Insituform™ Gunnar Hognestad Principal Engineer guhog@statoil. com www. statoil. com 16 Classification: Internal 2010 -11 -19