A new international standard is in the final draft stage of preparation and should be published as a fully fledged standard by 2004. This new standard is the result of a six-year effort by NACE, EFC and ISO/TC 67/WG 7. The standard is based, in the main, upon NACE MR0175 and the European Federation of Corrosion Reports 16 and 17. The new standard provides methods for the qualification and selection of metals resistant to cracking in sour oil and gas production. The paper describes the background to the development of the new standard and provides a brief summary of its contents with the aim of outlining its impact on materials selection for those already familiar with previous documents. The paper also describes the make up and working of the ISO 15156 Maintenance Panel that will provide for the continuous maintenance of the document.
Shortly after World War II, the need for natural gas was recognized and the oil and gas industry began an exploration program to provide the needed gas. Unfortunately, some of the gas reserves found contained hydrogen sulfide (H2S) and this caused sulfide stress cracking (SSC) failures in some of the metals used in production equipment. Most of the initial failures occurred in Texas and Western Canada. At the request of the Companies involved, the National Association of Corrosion Engineers (NACE) formed a Committee in 1950 to help understand and avoid these failures. They reported the results of the efforts of both suppliers and users in a NACE Report in 1952. ~ Because of the urgent need for gas supplies, drilling became very active in Alberta, Canada during the early 1950s. Subsequent equipment failures led to the formation of a joint Canadian industry task group to seek solutions to the problems. This group later became associated with NACE and provided a NACE Report, which was published in 1963. ~2~ Following that, NACE provided reports in 1963 and 1966 and the first standard in 1975. (3,4,5)
The first edition of this NACE Standard, MR-01-75, only covered valves and wellhead equipment. As a result of other equipment failures, a NACE Task group published a revised version of MR0175 in 1978 for a (6) broad range of equipment for sour oil and gas production. Many revisions have been published since 1978.
Several of the gas fields discovered contained as high as 50 mol% H2S often at high temperatures and pressures. These severe environments sometimes required both higher strength and more corrosion resistant metals than the carbon and low alloy steels used traditionally. For the past 20 years most of the research and MR0175 modifications have focused in this area. An effort was initiated in 1995 to review and update the corrosion resistant alloy (CRA) part of MR0175. The updated version provides new CRA information on acceptable environments and alloy choices.
A reconsideration of the scope of MR0175 was brought about by a number of factors. These included the introduction of seawater injection into oil reservoirs in North Sea oil fields allowing the bacterial breakdown of the sulfate in the seawater and causing HzS contamination of the produced oil and gas. An additional factor was the introduction of early types of controlled rolled steel plate for pipe and pressure vessels whose contact with H2S resulted in problems with hydrogen induced cracking (HIC). The European Federation of Corrosion (EFC) formed a committee to study the impacts of these and other issues on materials selection for H2S containing environments. Their findings are included in EFC Reports 16 and 17. (7,8) The preparation of an international standard making use of the NACE and EFC efforts was proposed in 1995. This proposal was accepted and a wor