October 18, 2010

Topic

Materials selection and recommendation is an important part of project development, that when looked back historically is rife with oddities that do not make sense. The oddities were often done because of cost savings, to use a different corrosion resistant alloy (CRA) instead of a preferred one or carbon steel, but the specifics are often not captured and go against many of the precepts of materials selection.

Some standards and guidance do exist for CRAs, but many experts have slightly differing opinions as to the actual environmental conditions were some of these materials are acceptable for use. This makes it more challenging to perform a materials selection for more complex conditions and for a good transfer of knowledge to occur when these materials are required.

Of all the CRAs used in oil and gas projects, martensitic stainless steels are the most common due to usability, cost, and availability, but some of the acceptable limits for these steels are not well defined. Using published data, an analysis was developed to better estimate the SSC susceptibility use of M13Cr-110 tubular goods in sour and souring conditions using NACE TM 0177 Method A tests. This data contained test conditions and results from multiple different mills and third party labs, and was organized to prevent any preferential treatment. Unlike most domain diagrams which are grouped by chloride contents, data was grouped by pH and compiled. When the data was plotted, an empirical SSC susceptibility estimation diagram was formed. This diagram was compared with existing domain diagrams and showed decent correlation with them. Diagrams similar to this can be developed to aid with materials selection and recommendation as the environmental conditions become more severe, the challenges to reduce costs increase, and provide a more rapid means to transfer knowledge.

Bio

Eric Caldwell is a veteran of the United States Navy’s submarine force having served on two separate classes of submarines. Honorably discharged and enrolled at the University of Florida where he received BS and MS degrees in Materials Science and Engineering specializing in 4th generation Ni-based single crystal superalloys for gas turbines. Instead of going into aerospace as planned, he shifted to the oil and gas industry to work for ExxonMobil Development, where he worked as a Materials Specialist and a subject matter expert on corrosion resistant alloys and tubular goods. He is currently with GATE, LLC where he is responsible for metallurgy and cracking. He is a member of several NACE committees including TG 299, the NACE MR 0175/ISO 15156 Oversight committee.