Bp-Operator’s Views of Current Status and Future Research -H2S Cracking

8/20/2019 Bp-Operator’s Views of Current Status and Future Research -H2S Cracking

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Operator’s views of current status andfuture research - H2S Cracking

John Martin

BP Exploration


2/26

Sour Service (H2S Cracking)

• Definition:-

− ISO 15156

‘Exposure to oilfield environments that contain H2S

and can cause cracking of materials by themechanisms addressed by ISO 15156 Part 1’

• Mechanisms in ISO 15156

−SSC, HIC, SOHIC, SZC, SCC, GHSC


3/26

Generation of Hydrogen by Corrosion Processes

Fe2+

Fe – 2e

2H++2e =H.+H

.=H2

H.

H.+H

.=H2


4/26

Hydrogen Entry Mechanism

• Atomic Hydrogen is generated by the corrosionprocess

• Generally H• + H• = H2

• However HS- poisons the combination.

• H• enters the steel matrix


5/26

Cracking in sour service

H

HHH

H

Higher Strength Steels YS > 500 MPa Low Strength Steels YS < 550 MPa

Applied Stress No Applied Stress

H2

H2

H2 H+

S2-Fe2+

H

H

FeS Film

Metal Matrix

pH 2S

pH


6/26

Sulphide Stress Cracking (SSC)

• Cracking involving corrosion and tensile stress in the

presence of water and H2S

• Hydrogen embrittlement mechanism in carbon steel


7/26

Low Alloy Steel Grades (API 5CT/ISO11960)

Strength

(ksi)

Grade

(ISO 11960

except *) Min. Yield Max. Yield Min. Tensile

H40 40 80 60 Yes

J55 55 80 75 Yes

K55 55 80 95 Yes

M65 65 85 85 Yes

C90 90 105 100 No (?)

L80 80 95 95 Yes

C95 95 110 105 No (?)

P110 110 140 125 No (?)

C110* 110 120 115 Mild Only

Q125 125 150 135 No (Type 1 (?))

T95 95 110 105 Yes

N80 80 110 100 No (?)

C125* 125 140 130 Very Mild Only

H2S

Resistant


8/26

Domain Diagram for C110


9/26

Low Alloy Steel Grades (API 5L/ISO3183)

Strength

(ksi)

Grade

(* new

additions)Min. Yield Max. Yield Min. Tensile

B 35 65 60 Yes

X42 42 72 60 Yes

X46 46 76 63 Yes

X60 60 82 75 Yes

X56 56 79 71 Yes

X65 65 87 78 Yes

X80 80 140 125 No (?)

X90* 90 112 101 No (?)

X100* 100 122 110 No (?)

X70 70 92 83 Yes

X52 52 77 67 Yes

X120* 120 152 133 No (?)

H2S

Resistant


10/26

Hydrogen Induced Cracking (HIC)

• Cracking that occurs when atomic hydrogen diffuses into steel and

combines to form molecular hydrogen at discontinuities• Also called Hydrogen Pressure Induced Cracking (HPIC); Blister

cracking; Stepwise cracking (SWC)30” seam welded API 5LX 60 sourcrude oil pipeline, failed 1972 during

commissioning. Abu Dhabi

Also called “step-wise

cracking”


11/26

HIC and Related Mechanisms in ISO15156/NACEHIC and Related Mechanisms in ISO15156/NACEMRMR--01750175

““The equipment user shall consider HIC/SWCThe equipment user shall consider HIC/SWC

as defined in ISO 15156as defined in ISO 15156--1/NACE MR1/NACE MR--01750175when evaluating flatwhen evaluating flat--rolled carbon steelrolled carbon steel

products for sour service environmentsproducts for sour service environments

containing even trace amounts of Hcontaining even trace amounts of H22SS””


12/26

Preliminary proposal for HIC severity regions


13/26

CRA Grades (ISO 13680 except *)

Type Category

(Cr-Ni-Mo)

Maximum Available SMYS

(ksi)

13-0-0* (e.g. L80 13Cr) 90

25-7-3+N 125

27-31-4 140

21-42-3 125

25-50-6 140

20-54-9+17Fe 140

22-50-7 140

13-4-1* 110

Martensitic Stainless Steel

13-5-2 110

22-5-3+N 125

Super Duplex Stainless Steel 25-7-4 + 2W +N 125

Austenitic Stainless Steel

25-32-3 140

Austenitic Ni Al loys

15-60-16 +4W 140

Duplex Stainless Steel


14/26

13Cr/4Ni/1Mo alloy – SSC Failure


15/26

SSC Failure of Downhole Tubular String

• HP/HT Gas Producer – 45mmscf/d, 50ppm H2S and 8.7mol%CO2.(0.5psia H

2S, pH 3.5).

• Completed with a mixture of L80-13Cr & CR13 95ksi 13/4/1 tubing.

• Packerless completion allowed produced fluid to contact tubing OD.

• Tubing failed via SSC at localised sites of cold work on the OD (slip andtong marks).

• Gas, water and sand flowed from the tubing bore to the annulus,resulting in significant erosion of both the tubing and casing.


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Domain Diagram for Super 13Cr

pH

3.5

4.5

5.5

0.001 0.01 0.1 1.0

pH2S (bara)

Domain Diagram For The Sulphide Stress Cracking Limits

Of 95ksi Super 13Cr Alloys In High Chloride (120,000 ppm Cl-

) Waters

UNACCEPTABLE

ACCEPTA BLE

0.03bara

FURTHER ASSESSMENT REQUIRED

pH

3.5

4.5

5.5

0.001 0.01 0.1 1.0

pH2S (bara)

Domain Diagram For The Sulphide Stress Cracking Limits

Of 95ksi Super 13Cr Alloys In High Chloride (120,000 ppm Cl-

) Waters

UNACCEPTABLE

ACCEPTA BLE

0.03bara

FURTHER ASSESSMENT REQUIRED


17/26

Stress Corrosion Cracking (SCC)

• In the context of this talk relates to the SCC

mechanisms that are associated with ‘active pathdissolution’ mechanisms (e.g. chloride SCC) and not

hydrogen-related mechanisms already covered (SSC,

HIC, etc.)

• As such the focus is mainly corrosion-resistant alloys

such as austenitic stainless steels (e.g. AISI 316),

duplex stainless steels (mixed mode mechanism or

CSC) and some nickel alloys (e.g. alloy 825)

• Developing domain diagrams for welded constructions

(flowlines, manifolds, piping,vessels, etc.) similar tothose already developed for OCTG


18/26

Domain diagrams for CRA flowlines and risers

pH

Partial Pressure

H2S

Decrease chloride,

temperature?

Increase chloride,

temperature?

No cracking

Cracking


19/26

Effect of welding?

pH

Partial Pressure

H2S


20/26

Cracking of duplex stainless steel

SSC D i f 25C D l St i l St l (125k i SMYS)


21/26

SSC Domain for 25Cr Duplex Stainless Steel (125ksi SMYS)


22/26

Areas of active research

• Effect of environmental conditions on cracking of CRAs

−

Chloride− Temperature

− pH

−H2S

• Effect of material processing on cracking

− Welding

− Plastic strain


23/26

H2S Cracking (SSC, SCC and HIC)

Thank You

For

Your

Attention!


24/26

SOHIC

3.5

mm


25/26

SOHIC

• Current Test Methods

−NACE TM0103 – Plate steels

− OTI 95 635 – Linepipe

• No universally accepted test method available• Bodycote/TWI/Force JIP

− Aim – To develop a simple go/no go SOHIC test

method for pressure vessel steels and line pipe


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SOHIC

• SOHIC testing requires further development

−JIP Test Method (Test Method imposes simultaneoustwisting and bending on a flat specimen to generate

triaxial stress)

−Methods for assessing fittings

• Appropriate test methods need to be applied

• Test techniques need to be realistic such that goodmaterials are accepted and poor ones rejected

Documents

Bp-Operator’s Views of Current Status and Future Research -H2S Cracking