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New Technology of CRA Linepipe

-- CONTENTSCONTENTS --

1.1. Why choose CRA for linepipes ?Why choose CRA for linepipes ?2.2. Previous technology of CRA linepipesPrevious technology of CRA linepipes3.3. New technology of CRA linepipesNew technology of CRA linepipes

4.4. Future development worksFuture development works55 . Conclusion. Conclusion

Masakatsu UedaSumitomo Metal Industries, Ltd.

Norway-Japan Seminar Milestones in onshore/offshore pipeline research, May, 27, 2003

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Why choose CRA for linepipes

Characteristic on Oil & Gas WellsCharacteristic on Oil & Gas WellsOil wells: In their early days,- Not to be highly corrosive with

protective oil film over thecarbon steel surface.

- As time passes, to produceincreasing amounts of water andto be rather corrosive.

Gas wells:- Not to have the same benefit of

protective oil film- To have the condensation ofwater from vapor in the gas.

- pH of the condensed water istypically between 3.5 and 4.5 andcorrosion rates of carbon steelcan be very high, sometimesseveral mm per year.

The use of chemical inhibitoradditions to well fluids

Examples of practical problems

- The well design is unsuitable forinjecting inhibitor

- The corrosion rate is too high, evenwith inhibitor injection.

- The cumulative cost of purchasinginhibitor year on year can becomeexcessive.

- High reliability is required in theinhibitor injection system which cannotalways be guaranteed.

- The environmental disposal issues withinhibitors are too demanding.

The use of CRA linepipes- To have higher reliability than carbon

steel with inhibition.

- To have lower life cycle cost andmuch less environmental impact

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Previous technology of CRA linepipes

Carbon steel

with inhibitor

Duplex stainless steel orClad

H2S High

C O 2

H i g h

T e m p e r a

t u r e

H i g h

Fig. Applicable Environmentsfor CRA linepipes(1975 to 1990 year)

For CO 2 + slightly H 2 S Environments(Strength grade: up to X65)

Duplex Stainless Steel(DSS) pipesUNS S31500: 18Cr-5Ni-3Mo

UNS S31803: 22Cr-5.5Ni-3Mo-0.1NClad pipes with cladding layer ofstainless steelUNS S31603: 18Cr-12Ni-3Mo(AISI 316L)

1975 1980 1985 1990 1995 2000

1,200

1,000

800

600

400

200

0 I n s

t a l l e

d l e n g

t h ( k m

)

Fig. Cumulative Use(km) of DSS and Clad pipes

DSS

Clad

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Key technology to prevent corrosionFor CO For CO

2 2 Corrosion (General and Localized Corrosion)Corrosion (General and Localized Corrosion) at elevated temp.at elevated temp.

Higher Cr content in steels,Higher Cr content in steels,Higher corrosion resistance due to Cr enrichment on surface f Higher corrosion resistance due to Cr enrichment on surface f ilmilm

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Key technology to prevent corrosion

For H For H 2 2 S Corrosion (Stress Corrosion Cracking: SCC) at room temp.S Corrosion (Stress Corrosion Cracking: SCC) at room temp.Higher Cr , Ni and Mo contents in steels,Higher Cr , Ni and Mo contents in steels,Higher SCC resistance due to forming stable dual surface filmHigher SCC resistance due to forming stable dual surface film

Corrosion mechanismCorrosion mechanism

Stable surface film formationStable surface film formation

- Prevention of localized corrosion

Forming stable surface film byHigher Cr, Ni and Mo content

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New New technology of CRA linepipes

C steel+ inhibitor

H2S High

C O 2

H i g h

T e m p e r a

t u r e

H i g h

Fig. Applicable Environmentsfor CRA linepipes(from 1990 year)

Super13Cr MS S

DSS

Clad

Strength grade: up to X80

Weldable Super 13Cr MartensiticStainless Steel seamless linepipes

(1) Superior corrosion resistance toCO 2 and slightly H 2S environments

(2) Quite cheap to DSS and Clad

Improved-Duplex Stainless Steel(DSS)and Clad pipesCorrosion resistance to(1) Seawater & Slightly H 2S for DSS

(2) Highly H 2S for Clad

Fig. Cumulative Use(km) of Super 13Cr MSS, DSS and Clad pipes1975 1980 1985 1990 1995 2000

1,200

1,000

800

600

400

200

0 I n s

t a l l e

d l e n g t

h ( k m

) DSS

Clad

Super 13CrMSS

Fig. % share in 2000 t0 2002

Super 13Cr MSS(66%)

Clad(28%)DSS(6%)

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Weldable Super 13Cr Martensitic Stainless SteelsSeamless Linepipes - Material development -

The development of weldable Super 13Cr MSS has been carried out byparallel activities of the following technical development together withNorwegian oil company, Statoil in 1993 to 1995 years;

1) Base metalAlloy design of base metal to keep corrosion resistancefor CO 2 and slightly H 2S

Ultra low Carbon MSS to adjust Cr, Ni, Mo, Ti contents

2) Welding wireAlloy design of weld metal to keep YS and toughness with low H content

Super DSS to adjust Cr, Ni, Mo and N contents

3) Welding procedureHigh speed welding technique,

Pulsed MIG welding method has been developed by Statoil

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Weldable Super 13Cr Martensitic Stainless SteelSeamless Linepipes - Alloy design concept -

Key technologyKey technology- Ultra low Carbon : less than 0.01%

- Welding material : Super duplex stainless steel(DP3W)

X80 weldable,with over matchingwelding materials

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Weldable Super 13Cr Martensitic Stainless SteelSeamless Linepipes - Mechanical properties -

Welding procedure (GTAW: 1.2kJ/mm)

Hardness distribution(almost the same from base metal to weld metal)

Tensile strength (satisfy X80 Spec.)

Toughness (Excellent)

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Weldable Super 13Cr Martensitic Stainless SteelSeamless Linepipes - Corrosion resistance -

Super 13Cr

weldment

For CO For CO 2 2 at elevated temp.:at elevated temp.:

General & localized corrosion

For H For H 2 2 S at room temp.:S at room temp.:

Sulfide Stress Corrosion Cracking

3.0MPa CO 2 + 0.001MPa H 2S, 5%NaCl, 100%YS, 336h SSRT: 3.0MPa CO 2 + x H 2S

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Future development worksFuture development works-- WeldableWeldable super 13Cr msuper 13Cr martensitic stainless steel seamlessstainless steel seamless linepipeslinepipes --

Optimization of Application technology

Intergranular Stress Corrosion Cracking at Elevated TemperatureSCC mechanism on HAZ of super 13Cr MSS in CO 2 environments at elevated

temperature will be made clear, though the SCC can be prevented by theapplication of post weld heat treatment( PWHT).The SCC in no PWHT conditions occurs on the HAZ of intact root surface, butdoes not as the intact root surface is machined.

Hydrogen Emblittlement

1) Pre-serviceThe combination of a high strength material, the presence of various differentmicrostructure around the weld and not very well known stress/straindistributions in the weld area will be investigated for a more fundamentalapproach.

2) In-serviceSacrificial anodes, overprotection to lead to the development to leaks aroundanode attachments and moderate cathodic protection technique will beinvestigated for preventing hydrogen emblittlement.

Welding ProcedureThe development of chemically matching weld consumables and various girthwelding processes will be investigated for welding faster and cheaper.

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- Conclusion -

CRACRA linepipeslinepipes have some benefits of higher corrosion resistance,have some benefits of higher corrosion resistance,lower life cycle cost, and much less environmental impact thanlower life cycle cost, and much less environmental impact thancarbon steel with inhibition.carbon steel with inhibition.

WeldableWeldable super 13Crsuper 13Cr martensiticmartensitic stainless steel seamlessstainless steel seamless linepipeslinepipesof X80 grade with super duplex stainless weld metal have beenof X80 grade with super duplex stainless weld metal have beendeveloped by new technology of ultra low carbon and alloy designdeveloped by new technology of ultra low carbon and alloy designof Cr, Ni, Mo and Ti for COof Cr, Ni, Mo and Ti for CO 22 and slightly Hand slightly H 22S environments. And theS environments. And theapplication of these pipes has been substantial with approximateapplication of these pipes has been substantial with approximate lyly650 km and 66% share of CRA650 km and 66% share of CRA linepipeslinepipes in between 2000 and 2002.in between 2000 and 2002.

As future development works, optimization of applicationAs future development works, optimization of application

technology will be investigated for thetechnology will be investigated for the weldableweldable super 13Crsuper 13Crmartensiticmartensitic stainless steel seamlessstainless steel seamless linepipeslinepipes ..