Table Of ContentEuropean Federation of Corrosion
Publications
NUMBER 23
A Working Party Report on
Corrosion Control in Oil
CO 2
and Gas Production
Design Considerations
detidE yb
M. .B INAMREK & .L M. HTIMS
Published for the European Federation of Corrosion
by The Institute of Materials
THE INSTITUTE OF MATERIALS
1997
Book Number 688
Published in 1997 by The Institute of Materials
1 Carlton House Terrace, London SW1Y 5DB
© 1997 The Institute of Materials
All rights reserved
British Library Cataloguing in Publication Data
Available on application
Library of Congress Cataloging ni Publication Data
Available on application
ISBN 1-86125-052-5
Neither the EFC nor The Institute of Materials
is responsible for any views expressed
in this publication
Design and production by
SPIRES Design Partnership
Made and printed in Great Britain
European Federation of Corrosion Publications
Series Introduction
The EFC, incorporated in Belgium, was founded in 1955 with the purpose of
promoting European co-operation in the fields of research into corrosion and corro-
sion prevention.
Membership is based upon participation by corrosion societies and commit-
tees in technical Working Parties. Member societies appoint delegates to Working
Parties, whose membership is expanded by personal corresponding membership.
The activities of the Working Parties cover corrosion topics associated with
inhibition, education, reinforcement in concrete, microbial effects, hot gases and
combustion products, environment sensitive fracture, marine environments, surface
science, physico-chemical methods of measurement, the nuclear industry, computer
based information systems, the oil and gas industry, the petrochemical industry and
coatings. Working Parties on other topics are established as required.
The Working Parties function in various ways, e.g. by preparing reports,
organising symposia, conducting intensive courses and producing instructional
material, including films. The activities of the Working Parties are co-ordinated,
through a Science and Technology Advisory Committee, by the Scientific Secretary.
The administration of the EFC is handled by three Secretariats: DECHEMA
.e .V in Germany, the Soci6t6 de Chimie Industrielle in France, and The Institute of
Materials in the United Kingdom. These three Secretariats meet at the Board of
Administrators of the EFC. There is an annual General Assembly at which delegates
from all member societies meet to determine and approve EFC policy. News of EFC
activities, forthcoming conferences, courses etc. is published in a range of accredited
corrosion and certain other journals throughout Europe. More detailed descriptions
of activities are given in a Newsletter prepared by the Scientific Secretary.
The output of the EFC takes various forms. Papers on particular topics, for
example, reviews or results of experimental work, may be published in scientific and
technical journals in one or more countries in Europe. Conference proceedings are
often published by the organisation responsible for the conference.
In 1987 the, then, Institute of Metals was appointed as the official EFC
publisher. Although the arrangement is non-exclusive and other routes for publica-
tion are still available, it is expected that the Working Parties of the EFC will use The
Institute of Materials for publication of reports, proceedings etc. wherever possible.
The name of The Institute of Metals was changed to The Institute of Materials
with effect from I January 1992.
A. D. Mercer
EFC Series Editor,
The Institute of Materials, London, UK
viii Series Introduction
EFC Secretariats are located at:
Dr B A Rickinson
European Federation of Corrosion, The Institute of Materials, 1 Carlton House
Terrace, London, SWIY 5DB, UK
Mr P Berge
F6d6ration Europ6ene de la Corrosion, Soci6t6 de Chimie Industrielle, 28 rue Saint-
Dominique, F-75007 Paris, FRANCE
Professor Dr G Kreysa
Europ/iische F6deration Korrosion, DECHEMA e. V., Theodor-Heuss-Allee 25, D-
60486, Frankfurt, GERMANY
Preface
Corrosion is a natural potential hazard associated with oil and gas production and
transportation facilities. This results from the fact that an aqueous phase is normally
associated with the oil and/or gas. The inherent corrosivity of this aqueous phase is
then dependent on the concentration of dissolved acidic gases and the water chemistry.
The presence of H2S, CO ,2 brine and/or condensed water with the hydrocarbon not
only give rise to corrosion, but also can lead to environmental fracture assisted by
enhanced uptake of hydrogen atoms into the steel. CO 2 is usually present inproduced
fluids and, although it does not cause the catastrophic failure mode of cracking
associated with ,*S2H its presence can nevertheless result in very high corrosion rates
particularly where the mode of attack on carbon and low alloy steels is localised. In
fact CO 2 corrosion, or 'sweet corrosion', is by far the most prevalent form of attack
encountered in oil and gas production and is a major source of concern in the
application of carbon and low alloy steels. Hence, the need to have a document which
systematically addresses the steps, considerations and parameters necessary to
design oil and gas facilities with respect to CO 2 corrosion.
This document sets the scene on design considerations specifically related to CO 2
corrosion. It has been developed from feedback of operating experience, research
results and operators' in-house studies. Particular attention has been given to the
chemistry of the produced fluid, the fluid dynamics and physical variables which
affect the performance of steels exposed to CO2-containing environments. The focus
is on the use of carbon and low alloy steels as these are the principal construction
materials used for the majority of facilities in oil and gas production offering
economy, availability and strength.
This document is a practical, industry oriented guide on the subject for use by
design engineers, operators and manufacturers. It incorporates much of the recent
developments in the understanding of the ways in which detailed environmental and
physical conditions affect the risk of CO 2 corrosion. It also describes means of
corrosion control. It is comprehensive in addressing CO 2 corrosion of all major items
of oilfield equipment and facilities incorporating, production, processing and
transportation. As such, it provides a key reference for materials and corrosion
engineers, product suppliers and manufacturers working in the oil and gas industry.
*'Sour corrosion', resulting from the presence of H2S, is the subject of EFC Publications Numbers 61
and .71
stnemegdelwonkcA
The CO 2 Corrosion Work Group of the EFC Working Party on Corrosion in Oil and
Gas Production held its first meeting in September 1993. Since then, several meetings
have been held to address industry-wide issues related to engineering design for CO 2
corrosion. The organisation of the Work Group was undertaken by representatives
from worldwide oil and gas producers, manufacturers, service companies and
research institutions.
In achieving the primary objective, parameters affecting CO 2 corrosion, its
mechanism and methods of control have been discussed during the Work Group
meetings. These aspects form the core of the present document, Sections of which
have been prepared by the Work Group members.
The chairmen of the Working Party and Work Group would like to thank all who
have contributed their time and effort to ensure the successful completion of this
document. In particular we wish to acknowledge a significant input from these
individuals and their respective companies:
J Pattinson, A McMahon and D Harrop, ,PB UK
J-L Crolet, Elf, France
A Dugstadt, IFE, Norway
G Schmitt, MFI, Germany
Y Gunaltun, Total, France
E Wade, previously with Marathon, UK
O Strandmyr, Statoil, Norway
W Lang, Bechtel, UK
J Palmer, CAPCIS, UK
M Swidzinski, Phillips, UK
M Celant, MaC, Italy
P O Gartland, CorrOcean, Norway
R S Treseder, CorrUPdate, USA
J Kolt, Conoco, USA
N Farmilo, AEA Technology, UK
In addition, valuable comments from R Connell and B Pots (Shell, The Netherlands)
and T Gooch (TWI, UK) are appreciated.
Finally, one of the editors (MBK) wishes to thank BP for their support and
permission to publish some of the information in this document.
Bijan Kermani Liane Smith
Chairman of CO 2 Corrosion Chairman of EFC Working Party on
Group Workshop Corrosion in Oil and saG Production
Contents
Series Introduction ................................................................................................................ vii
Preface ................................................................................................................... , ................ ix
Acknowledgements .................................................................................................................. x
1 Introduction ............................................................................................................... 1
2 Scope ........................................................................................................................... 3
3 The Mechanism of CO2 Corrosion ........................................................................ 4
4 Types of CO2 Corrosion Damage .......................................................................... 6
4.1. Localised Corrosion of Carbon Steel ............................................................... 6
4.2. Localised Corrosion of Carbon Steel Welds ................................................... 7
5 Key Parameters Affecting Corrosion .................................................................... 9
5.1. Water Wetting ..................................................................................................... 9
5.1.1. Water Characteristics ................................................................................ 10
5.1.2. Hydrocarbon Characteristics ................................................................... 10
5.1.3. Top-of-the-Line Wetting ........................................................................... 11
5.2. Partial Pressure and Fugacity of ....................C...O.... .......................................2 .................... 12
5.3. Temperature ...................................................................................................... 12
5.4. pH ....................................................................................................................... 14
5.5. Carbonate Scale ................................................................................................. 15
5.6. The Effect Of H2S ............................................................................................... 15
5.7. Wax Effect .......................................................................................................... 16
Prediction of the Severity of CO2 Corrosion .................................................... 18
6.1. CO 2 Corrosion Prediction Models For Carbon Steel ................................... 19
CO2 Corrosion Control .......................................................................................... 24
7.1. Micro-alloying of Carbon and Low Alloy Steels ......................................... 24
7.1.1. Effect of Chromium ................................................................................... 24
7.1.2. Effect of Carbon ......................................................................................... 25
7.1.3. Effect of Other Alloying Elements .......................................................... 25
7.2. Effect of Glycol and Methanol ........................................................................ 26
vi Contents
7.3. pH Control ......................................................................................................... 27
7.3.1. The Role of pH ........................................................................................... 27
7.3.2. Wet Gas Transportation Lines ................................................................. 27
7.3.3. Different Chemicals and Their Mechanisms ......................................... 27
7.3.4. pH Monitoring ........................................................................................... 28
7.4. Corrosion Inhibition ......................................................................................... 28
7.4.1. Inhibitor Mechanism ................................................................................. 29
7.4.2. Inhibitor Efficiency and Inhibitor Performance .................................... 30
7.4.3. Inhibitor Partitioning and Persistency ................................................... 31
7.4.4. Commercial Inhibitor Packages ............................................................... 34
7.4.5. Inhibitor Compatibility ............................................................................. 34
7.4.6. Inhibitor Deployment ............................................................................... 35
7.4.7. Inhibitor Distribution in Multiphase Pipelines ..................................... 36
7.4.8. Effect of Flow on Inhibition ..................................................................... 36
8 Corrosion Allowance Determination ................................................................. 37
8.1. Design Corrosion Allowance .......................................................................... 38
8.1.1. Design Corrosion Rate .............................................................................. 38
8.1.2. Design Corrosion Allowance Assessment ............................................ 38
9 Design Considerations .......................................................................................... 41
9.1 Well Completions .............................................................................................. 41
9.1.1. Corrosion Design ....................................................................................... 42
9.1.2. Corrosion Monitoring ............................................................................... 43
9.2. Production Facilities ......................................................................................... 44
9.2.1. Corrosion Design ....................................................................................... 44
9.2.2. Multiphase Fluid Behaviour .................................................................... 46
9.2.3. Corrosion Monitoring ............................................................................... 47
9.3 Gas Reinjection ................................................................................................... 49
9.3.1. General Requirements for Gas Reinjection ............................................ 49
9.3.2. Onshore Delivery Lines ............................................................................ 49
9.3.3. Offshore Delivery Lines ............................................................................ 50
9.3.4. Injection Wells And Gas Lift Annuli ...................................................... 50
References ............................................................................................................................ 51
European Federation of Corrosion Publications
Series Introduction
The EFC, incorporated in Belgium, was founded in 1955 with the purpose of
promoting European co-operation in the fields of research into corrosion and corro-
sion prevention.
Membership is based upon participation by corrosion societies and commit-
tees in technical Working Parties. Member societies appoint delegates to Working
Parties, whose membership is expanded by personal corresponding membership.
The activities of the Working Parties cover corrosion topics associated with
inhibition, education, reinforcement in concrete, microbial effects, hot gases and
combustion products, environment sensitive fracture, marine environments, surface
science, physico-chemical methods of measurement, the nuclear industry, computer
based information systems, the oil and gas industry, the petrochemical industry and
coatings. Working Parties on other topics are established as required.
The Working Parties function in various ways, e.g. by preparing reports,
organising symposia, conducting intensive courses and producing instructional
material, including films. The activities of the Working Parties are co-ordinated,
through a Science and Technology Advisory Committee, by the Scientific Secretary.
The administration of the EFC is handled by three Secretariats: DECHEMA
.e .V in Germany, the Soci6t6 de Chimie Industrielle in France, and The Institute of
Materials in the United Kingdom. These three Secretariats meet at the Board of
Administrators of the EFC. There is an annual General Assembly at which delegates
from all member societies meet to determine and approve EFC policy. News of EFC
activities, forthcoming conferences, courses etc. is published in a range of accredited
corrosion and certain other journals throughout Europe. More detailed descriptions
of activities are given in a Newsletter prepared by the Scientific Secretary.
The output of the EFC takes various forms. Papers on particular topics, for
example, reviews or results of experimental work, may be published in scientific and
technical journals in one or more countries in Europe. Conference proceedings are
often published by the organisation responsible for the conference.
In 1987 the, then, Institute of Metals was appointed as the official EFC
publisher. Although the arrangement is non-exclusive and other routes for publica-
tion are still available, it is expected that the Working Parties of the EFC will use The
Institute of Materials for publication of reports, proceedings etc. wherever possible.
The name of The Institute of Metals was changed to The Institute of Materials
with effect from I January 1992.
A. D. Mercer
EFC Series Editor,
The Institute of Materials, London, UK
viii Series Introduction
EFC Secretariats are located at:
Dr B A Rickinson
European Federation of Corrosion, The Institute of Materials, 1 Carlton House
Terrace, London, SWIY 5DB, UK
Mr P Berge
F6d6ration Europ6ene de la Corrosion, Soci6t6 de Chimie Industrielle, 28 rue Saint-
Dominique, F-75007 Paris, FRANCE
Professor Dr G Kreysa
Europ/iische F6deration Korrosion, DECHEMA e. V., Theodor-Heuss-Allee 25, D-
60486, Frankfurt, GERMANY
