Stainless steels have a great variety of potential applications in the petroleum industry, mainly as an alternative to carbon steel in corrosive environments. Within a number of media that can cause corrosion problems with these materials, only chloride solutions and hydrogen sulfide are of importance in oilfield service.A reliable tool that permits the proper selection of stainless steels has yet been missing. In order to provide engineering diagrams for this purpose, pitting and stress corrosion cracking (SCC) tests were performed. Specimens were exposed to NaCl solutions containing from 3 to 100,000 ppm Cl À at temperatures from 40 to 200 8C. This test configuration was chosen to give a better representation of actual service conditions than accelerated standard test procedures do.Tested materials were the austenitic stainless steel grades 321, 316Ti (API LC30-1812) and 254 SMO, and 22Cr duplex (austenitic-ferritic) steel (API LC65-2205). Based on an optical examination of the specimens, no-risk regions of chloride concentration vs. temperature have been identified. Subsequently, service temperature limits have been deduced for each tested material.Thus, material failures by pitting and SCC can be prevented without overdesigning. The results of the testing series are applicable to all chloride environments without presence of H 2 S, as they have to be handled by primary production equipment, as well as transportation and gas processing facilities.Nichtrostende Stähle haben ein großes Anwendungspotential in der Ö l-und Gasindustrie, da sie eine Alternative zu Kohlenstoffstahl in korrosiver Umgebung darstellen. Von den Medien, in denen Korrosionsprobleme mit nichtrostenden Stählen auftreten könnten, spielen in der Ö l-und Gasindustrie nur chloridhaltige Lösungen und Schwefelwasserstoff eine Rolle.Bisher gab es keine zuverlässige Möglichkeit zur richtigen Auswahl eines geeigneten nichtrostenden Stahls. Lochkorrosions-und Spannungsrisskorrosionstests (SCC) wurden durchgeführt, um Auswahldiagramme erstellen zu können. Probekörper wurden in NaCl-Lösungen mit Chloridgehalten zwischen 3 und 100 000 ppm und bei Temperaturen von 40 bis 200 8C ausgelagert. Diese Testanordnung wurde gewählt, weil sie die Betriebsbedingungen besser repräsentiert als beschleunigte Standardtestverfahren.Die getesteten Werkstoffe waren die Austeniten 321, 316Ti (API LC30-1812) und 254 SMO und ein 22Cr Duplexstahl (API LC65-2205). Basierend auf einer optischen Auswertung der Proben wurden Chloridkonzentrationen in Abhängigkeit von der Temperatur identifiziert, die kein Risiko hinsichtlich eines Lochfraßes bzw. einer Spannungsrisskorrosion darstellen. In Folge konnten Betriebstemperaturlimits für jedes getestete Material abgeleitet werden.Mit Hilfe dieser Kurven können Werkstoffprobleme auf Grund von Lochkorrosion oder Spannungsrisskorrosion vermieden werden, ohne ein Overdesign vorzunehmen. Die Ergebnisse der Testreihen sind für alle chloridhaltigen Medien in Abwesenheit von H 2 S anwendbar, vom Produktionsequipment über die Transportleitungen...

In petroleum production, the problem of corrosive media attacking metallic structures is almost ubiquitous. Particularly severe environments are encountered in the production and transport of wet natural gas containing corrosive components, such as hydrogen sulphide and carbon dioxide. When exploring new gas fields, it is therefore a prerequisite to take into account the corrosivity of the respective fluids in all stages of the field development, material selection, field layout, and facilities design. In preparation of the subsequent production phase, reliable corrosion monitoring programs have to be selected, established, and implemented as necessary. Furthermore, the financial aspects always play an important role, thus posing a real challenge for the engineer forced to seek a compromise between economics and design.This paper gives a comprehensive overview of these considerations regarding four different OMV gas fields, two in Austria and two in Pakistan, which were successfully developed and brought onstream between 1967 and 2003. These fields not only vary in their geographical position, but also in their gas compositions, production start, and the location of gas dehydration units.One major aspect dealt with in each of these cases was material selection, including metallic as well as nonmetallic and composite materials. Where the initial decision was made in favor of carbon steel, different methods of corrosion protection, the application of corrosion inhibitors, corrosion monitoring, and intelligent pigging are discussed in the paper.A comparison of the various methods of resolution worked out for all four case histories, as well as the experience gained in more than three decades of production and transportation of wet, corrosive natural gas is presented.Furthermore, results of the ongoing corrosion monitoring measurements in operation in the mature gas fields are discussed under the aspect of the remaining facility lifetimes.

fax 01-972-952-9435. AbstractStainless steels have a great variety of potential applications in the petroleum industry, mainly as an alternative to carbon steel in corrosive environments. Within a number of media that can cause corrosion problems with these materials, only chloride solutions and hydrogen sulfide are of importance in oilfield service.A reliable tool that permits the proper selection of stainless steels has yet been missing. In order to provide engineering diagrams for this purpose, pitting and stress corrosion cracking (SCC) tests were performed. Specimens were exposed to NaCl solutions containing from 3 to 100,000 ppm Clat temperatures from 40 to 200 °C. This test configuration was chosen to give a better representation of actual service conditions than accelerated standard test procedures do.Tested materials were the austenitic stainless steel grades 321, 316Ti (API LC30-1812) and 254 SMO, and 22Cr duplex (austenitic-ferritic) steel (API LC65-2205). Based on an optical examination of the specimens, no-risk regions of chloride concentration vs. temperature have been identified. Subsequently, service temperature limits have been deduced for each tested material.Thus, material failures by pitting and SCC can be prevented without overdesigning. The results of the testing series are applicable to all chloride environments without presence of H 2 S, as they have to be handled by primary production equipment, as well as transportation and gas processing facilities.

In petroleum production, the problem of corrosive media attacking metallic structures is almost ubiquitous. Particularly severe environments are encountered in the production and transport of wet natural gas containing corrosive components, such as hydrogen sulphide and carbon dioxide. When exploring new gas fields, it is therefore a prerequisite to take into account the corrosivity of the respective fluids in all stages of the field development, in material selection, field layout, and facilities design. In preparation of the subsequent production phase, reliable corrosion monitoring programmes have to be selected, established, and implemented, as necessary. Furthermore the financial aspects always play an important role thus posing a real challenge for the engineer forced to seek a compromise between economics and design. This paper gives a comprehensive overview of these considerations regarding four different OMV gas fields, two of them in Austria and two in Pakistan, which were successfully developed and brought on stream between 1967 and 2003. These fields do not only vary in their geographical position, but also in gas compositions, production start, and the location of gas dehydration units. One major aspect dealt with in each of these cases, was material selection including metallic as well as non-metallic and composite materials. Where the initial decision was made in favour of carbon steel, different methods of corrosion protection, the application of corrosion inhibitors, corrosion monitoring, and intelligent pigging are discussed in the paper. Comparing the various methods of resolution that have been worked out for all four case histories, experience gained in more than three decades of production and transportation of wet corrosive natural gas is presented. Furthermore, results of the ongoing corrosion monitoring measurements in operation in the mature gas fields are discussed under the aspect of the remaining facility lifetimes. Introduction To achieve long lifetimes of the production facilities the production and transportation of wet corrosive natural gas requires selection of suitable material and measures for combating corrosion. In addition to the liquid phase which may show a low pH-value and some amount of chlorides the existence of the corrosives CO2 and H2S in the gaseous phase can pose serious corrosion problems. The presence of H2S, leads to the problem of general corrosion additionally it can lead to stress corrosion cracking (SCC) if the materials are not properly selected. Furthermore some operational parameters such as chlorides in the produced water and high temperatures can intensify the corrosivity of the fluids. Stress corrosion cracking is taken to be one of the most dangerous forms of corrosion because it can result in an unexpected failure of a component causing shutdown times and high financial losses due to the need for extensive repair or reinstallation e.g. of a pipeline but above all it can cause a potential environmental and safety risk as well. Carbon dioxide sweet corrosion is also a well known problem in gas production. CO2 dissolves in brine to form carbonic acid that ionizes to yield a low pH-value. The resulting acidic solution strongly enhances the corrosion in the carbon steel pipes and facilities. The presence of CO2 may lead to corrosion rates of several mm/year if no proper corrosion protection measures are applied. In principle, 3 ways to prevent corrosion can be distinguished:Use of inhibitors to protect carbon steel installationsUse of corrosion resistant alloys (CRA)Use of a combination of carbon steel and inhibitors, as well as CRA for critical partsUse of composite materials The advantages of corrosion inhibitors are well known to many involved in oil and gas business. In many cases it is a very economic method of achieving corrosion protection.

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