corrosion rate modelling - institute of materials ... 2019... · introduction. corrosion modelling...
TRANSCRIPT
Corrosion Rate Modelling
Educational Material from the IOM3
Energy Transition Group
The global network for the materials cycle
Introduction
• The Institute of Materials, Minerals & Mining (IOM3) is a major UK professional engineering institution, incorporated by Royal Charter, with over 15,000 members spread across the world.
• IOM3 exists to promote & develop all aspects of: materials science & engineering, metallurgy, geology, mining & associated technologies and petroleum engineering, as a leading authority in the global materials & natural resource community
• The Energy Transition Group represents over 800 members of the Institute who are interested in the Energy and related sciences.
• Membership of IOM3 provides a range of benefits, including access to globally recognised UK professional engineering qualifications such as Chartered engineer (CEng), go to: www.iom3.org
• This slide pack is part of a series of educational material produced by the Energy Transition Group to provide the Public with information on the production of oil and gas. The IOM3 accepts no responsibility for the contents of this slide pack.
INTRODUCTION
CO2 MODELLING SOFTWARE
HOW TO USE CALCULATED CORROSION RATE
A BIT ABOUT H2S CORROSION
O2 CORROSION MODELLING
SUMMARYSECTION B
2019 – DR MUHAMMAD EJAZ 3
AGENDA
This presentation covers• Carbon steel - not Corrosion Resistant Alloys• Linear corrosion mechanism (general corrosion) – not cracking
• Objective is to:
• Provide an overview of corrosion modelling• Avoid black box approach – “Computer says…..”• Use engineering judgment with numbers• Understand limitation of modelling
2019 – DR MUHAMMAD EJAZ 4
Scope and Objectives
Corrosion Modelling covers complete life cycle of a plant• Design of new facilities
- Materials Selection(C-steel vs CRA)
- Corrosion barrier requirements(Inhibition, coating,CP etc.)
2019 – DR MUHAMMAD EJAZ 5
Introduction
Introduction
Corrosion Modelling covers complete life cycle of a plant• Integrity Management
- React to changes in process conditions- New facility tie-in
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Introduction II
Corrosion Modelling for Oil and Gas
• CO2 Corrosion• H2S Corrosion• O2 Corrosion
• Anodic Reaction
Fe ↔ Fe2+ + 2e-
• Cathodic Reaction(s)
CO2 + H2O ↔ H2CO3 + 2e- ↔ H2 + CO32- (CO2 Corrosion)
O2 + 4H+ + 4e- ↔ 2H2O (O2 corrosion)
H2S ↔ 2H+ + S2- (H2S Corrosion)2019 – DR MUHAMMAD EJAZ 7
Oilfield Corrosion
2019 – DR MUHAMMAD EJAZ 8Illustration courtesy of http://duoline.blogspot.com/
CO2 CorrosionGeneral Corrosion Raindrop attack - gas condensate
Mesa-type corrosion
2019 – DR MUHAMMAD EJAZ 9Illustrations courtesy of octane.nmt.edu/
Types of Predictive Models
• Mechanistic- Formulated from quantitative knowledge of reactionthermodynamic and kinetics
• Empirical- Formulated from array ofexperimental measurements
• Semi-empirical- Mix of Above
2019 – DR MUHAMMAD EJAZ 10Illustration courtesy ofNACE Corrosion Handbook
Pioneering Work
De Waard and Milliams (Carbonic Acid Corrosion of Steel,1975)
log Vcorr = 5.8 - (1710 / (273 + T)) + 0.67 log (P𝑪𝑪𝑪𝑪𝟐𝟐
)
whereVcorr is corrosion rateT is Temperature, and P𝐶𝐶𝐶𝐶2
is partial pressure of CO2
(cathode reaction: H2CO3 reduction)
2019 – DR MUHAMMAD EJAZ 11Ref: C. DE WAARD, D. E. MILLIAMS, Carbonic Acid Corrosion of Steel, CORROSION. 1975;31(5):177-181
Partial pressure of a gas
• Partial pressure quantifies gas dissolved inwater at equilibrium- Total pressure * Mole fraction in gas
For example:For 0.1% CO2 in gas at pressureof 10 bara
P𝐶𝐶𝐶𝐶2
= 10 * 0.1 = 1 bara
- Ideal gas – Henry’s law
- Fugacity correction
2019 – DR MUHAMMAD EJAZ 12Ref: Bondos et. Al: Accurate corrosion prediction through an integrated approach, SPE 111430, 2006
Effect of acid gases on pH
• pH is function of- Partial pressure of acid gases
- Temperature
- Organic acid (Acetates)
- Formation water chemistrye.g., bicarbonate ion (HCO3
-)
- Formation water >~ 4.5
- Condensed water >= 3.5
2019 – DR MUHAMMAD EJAZ 13Ref: Corros. Sci. 1987, 27 pp. 1059–1070
Temperature – scale formation
• About 60 - 70°C carbonate scale start forming oncarbon steel surface
Fe + H2O + CO2 ↔ FeCO3 (Siderite) + H2
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De Waard & Milliams Nomogram
CRscale = CRfree x SF → Use a ruler to estimate corrosion rate
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Development of Predictive Model Software
Main inputs
• pH
• Scale
• Steel composition
• Glycol %
• Inhibition
• Wettability
• Organic acids (ppm)
2019 – DR MUHAMMAD EJAZ 16Ref: Joint industry projects at IFE 1998 – 2008 (EFC report in 2007/8)
NORSOK M-506 (2005)
• Input
• Limitations
• Output
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Comparison of Predictive models
ƒ Temperature ƒ pH
ƒ Pressure
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Illustration Ref: https://www.gateinc.com/gatekeeper/gat2004-gkp-2014-03
Using Predictive model out put
Corrosion allowance (mm)• Calculated corrosion rate x design life
If corrosion allowance is more than 10 mm for carbon steel –consider using corrosion resistant alloys (NORSOK M-001)
• Complete life cycle costanalysis with carbon steel+ inhibition
• Be aware of differentcorrosion rates (outputs)from different models
Carbon steel + inhibitor
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Example: Corrosion Allowance Calculation
p Corrosion Inhibitor 95% Pipe OD 219.1 mm 196.5 mm IDDesign Life 15 years WT 11.3 mm8" Production NDC ECE
Year Temperature PressureAverage Mol% CO2
Mol% H2S
Oil Flowrate
Water Flowrate
Gas Flowrate
pH Uninhibited Inhibited Inhibited
°C bara m3opd m3wpd sm3/d mm/yr mm/yr mm/yrPHACT BP93 DW93 BP95 DW95
1 1 67 73 6.50 0 2584 79 113267 4.4 0.8 1.2 0.9 1.0 20 1.1 0.11 11 67 73 0.89 0 2584 79 113267 5.3 0.2 0.3 0.2 0.2 2.7 0.2 0.012 1 67 73 6.50 0 3483 228 339802 4.4 0.8 1.2 1.2 1.4 23 1.2 0.32 11 67 73 0.89 0 3483 228 339802 5.3 0.2 0.3 0.3 0.3 3 0.2 0.13 1 67 73 6.50 0 1048 1984 339802 4.4 0.8 1.2 1.2 1.3 22 1.2 1.83 11 67 73 0.89 0 1048 1984 339802 5.3 0.2 0.3 0.3 0.3 3 0.2 0.44 1 67 73 6.50 0 911 2411 339802 4.4 0.8 1.2 1.2 1.3 23 1.2 1.84 11 67 73 0.89 0 911 2411 339803 5.3 0.2 0.3 0.3 0.3 3 0.2 0.45 1 67 73 6.50 0 804 2443 339802 4.4 0.8 1.2 1.2 1.3 23 1.2 1.85 11 67 73 0.89 0 804 2443 339803 5.3 0.2 0.3 0.3 0.3 3 0.2 0.46 1 67 73 6.50 0 578 2926 311485 4.4 0.8 1.2 1.2 1.3 23 1.2 1.86 11 67 73 0.89 0 578 2926 311486 5.3 0.2 0.3 0.3 0.3 3 0.2 0.47 1 67 73 6.50 0 470 3070 311485 4.4 0.8 1.2 1.2 1.3 23 1.2 1.87 11 67 73 0.89 0 470 3070 311486 5.3 0.2 0.3 0.3 0.3 3 0.2 0.48 1 67 73 6.50 0 340 3186 283169 4.4 0.8 1.2 1.2 1.3 22 1.2 1.78 11 67 73 0.89 0 340 3186 283170 5.3 0.2 0.3 0.3 0.3 3 0.2 0.39 1 67 73 6.50 0 291 3236 254852 4.4 0.8 1.2 1.1 1.2 22 1.2 1.79 11 67 73 0.89 0 291 3236 254853 5.3 0.2 0.3 0.3 0.3 3 0.2 0.3
10 1 67 73 6.50 0 240 3313 169901 4.4 0.8 1.2 1.0 1.1 21 1.1 1.610 11 67 73 0.89 0 240 3313 169902 5.3 0.2 0.3 0.2 0.3 2.9 0.2 0.311 1 67 73 6.50 0 196 3294 198218 4.4 0.8 1.2 1.1 1.2 22 1.2 1.611 11 67 73 0.89 0 196 3294 198219 5.3 0.2 0.3 0.2 0.3 2.9 0.2 0.312 1 67 73 6.50 0 164 3382 198218 4.4 0.8 1.2 1.1 1.2 22 1.2 1.612 11 67 73 0.89 0 164 3382 198219 5.3 0.2 0.3 0.3 0.3 2.9 0.2 0.313 1 67 73 6.50 0 154 3404 198218 4.4 0.8 1.2 1.1 1.2 22 1.2 1.613 11 67 73 0.89 0 154 3404 198219 5.3 0.2 0.3 0.3 0.3 2.9 0.2 0.314 1 67 73 6.50 0 135 3442 198218 4.4 0.8 1.2 1.1 1.2 22 1.2 1.614 11 67 73 0.89 0 135 3442 198219 5.3 0.2 0.3 0.3 0.3 2.9 0.2 0.315 1 67 73 6.50 0 121 3472 198218 4.4 0.8 1.2 1.1 1.2 22 1.2 1.615 11 67 73 0.89 0 121 3473 198219 5.3 0.2 0.3 0.3 0.3 2.9 0.2 0.3
4.3 6.2 5.0 5.3 4.8 5.9Required corrosion allowance
M-506
Cassandra Norsok
Inhibited Rate mm/yr
Basic Flow-sensitive
4.3 6.2 5.0 5.3 4.8 5.9Required corrosion allowance
Flow regimes in horizontal pipe
Example of steady-state flow regime map for a horizontal pipe.Superficial liquid velocity VL vs superficial gas velocity VG.
2019 – DR MUHAMMAD EJAZ 21Illustration Ref: http://www.drbratland.com/PipeFlow2/chapter1.html
Flow regimes play a critical role where inhibition is required or condensation may occur
Exploiting Output – Inhibition categorisation
B. Hedges, D. Paisley and R. Woollam, “The corrosion inhibitor availability model,” in Corrosion 2000. 2019 – DR MUHAMMAD EJAZ 22
H2S corrosion
H2S RegimeSour
pCO2 / pH2S = 20
pCO2 / pH2S = 500CO2 + H2S RegimeMixed
CO2 RegimeSweet
pCO2
pH2S
Losses typically localised corrosion.
Localised corrosion generally lower than rate predicted by CO2model.
CO2 model applies.
Carbon and low alloy steels
2019 – DR MUHAMMAD EJAZ 23Ref: NACE Corrosion Conference 02235, 06122 and 09564
Fe2S passive layer
CO2 only Corrosion rate
Fe2CO3 is protective scale above ~60C.
Fe2S is semi-protective layer and does not provide corrosion inhibition. This leads to localised corrosion.
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NACE Logigram
Metallurgy and Corrosion Control in Oil and Gas Production by Robert Heidersbach, 2011
Corrosion Modelling for Oil and Gas - II
• O2 Corrosion• Corrosion Product:
Geothite – FeO(OH)Hematite – Fe2O3
Magnetite – Fe3O4
Ferous Hydroxide – Fe(OH)2
• Anodic Reaction
Fe ↔ Fe2+ + 2e-
• Cathodic Reaction(s)
O2 + 4H+ + 4e- ↔ 2H2O (O2 corrosion)2019 – DR MUHAMMAD EJAZ 26
O2 Corrosion
Where:Co is the oxygen concentration in ppb,Uo is the fluid velocity in m/s,Re is the Reynolds number,Pr is the Prandtl number
(temperature dependant), andCr is Corrosion rate in mm/y.
Where:VCORR is the oxygen corrosion rate in mm/y,U is the fluid velocity in m/s [assumed U=1 if U<1],CO2 is the oxygen equivalent in ppm, andT is temperature in °C [assumed T=30 if T<30].
2019 – DR MUHAMMAD EJAZ 27OST and Salama Fischer O2 corrosion model. Graph Ref: Corrosion 960593 K.P. Fischer et al.
Summary
Various Corrosion prediction models are available
• Use corrosion prediction model with care andengineering judgment should always be applied.
• Always challenge and sense check the out put - Don’talways believe what “Computer says………..”.
• Understand the limitation of predictive models andcompare results from at least two models.
2019 – DR MUHAMMAD EJAZ 28