ABSTRACT

13%Cr alloyed Super Martensitic Stainless Steels (SMSS) are widely used as down-hole tubular products in the Oil & Gas industry. Optimization of the tubular material chemistry, cleanliness and manufacturing route has delivered useful sour service performance and application in a wide range of oil and gas projects. SMSS bar stock alloys are a common selection for the manufacturing of down-hole equipment, but their application remains restricted by sour service performance that is lower than can be achieved in the tubular product.

It is desirable, where strength requirement allows, to match the tubular grade for accessories and equipment. The sour service performance gap between SMSS tubular and bar stock makes this difficult for many fields. To explore if this gap could be overcome, development work was conducted to optimize the performance of 110ksi specified minimum yield strength UNS(1) S41426 bar product. Lessons learned in the manufacture of UNS S41426 tubulars and in the manufacture of high criticality bar products were combined to develop a bar manufacturing route to close the sour service performance gap. An initial operating window (as a function of pH, pH2S, dissolved chloride ion and temperature) has been established and is presented.

INTRODUCTION

ISO(2) 13680 / API(3) 5CRA Group 1 – Category 13-5-2 Super Martensitic Stainless Steel (SMSS) is widely used for downhole production tubing and liners in the Oil & Gas industry at strength levels of 95ksi and 110ksi specified minimum yield strength (SMYS). Optimization of the tubular material chemistry, cleanliness and manufacturing route has delivered useful sour service (sulfide stress cracking [SSC] and stress corrosion cracking [SCC]) performance, including for the 110ksi grade1,2,3,4. Note that whilst this present paper refers to grades by UNS number, these alloys are very sensitive to manufacturing process. Differences between manufacturers and even potentially manufacturing sites emphasizes that these are proprietary alloys with individual sour service limits and should be treated as such.

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