Abstract

This paper summarizes the experience with use of 3%Cr tubing material in production wells on a major oil field in the North Sea. Historically, API(1) 5CT grade L80 or API 5CT grade 13%Cr-80 production tubing was used on this field, but the corrosiveness of the production fluids indicated that an intermediate-alloyed material could be sufficient. In the search for a material with better corrosion resistance than the API 5CT Grade L80 steel and lower cost than API 5CT grade 13%Cr-80, 3%Cr alloyed steel was introduced as an option. Indications from the initial corrosion tests were that the 3%Cr could provide an increased life expectancy of up to about 5 times that of carbon steel. Further, the 3%Cr offered more than 30% cost reduction compared to the API 5CT grade 13%Cr-80. This paper summarizes the qualification testing/work performed to allow for use of 3%Cr-80 and the experience after more than 12 years in service.

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