Abstract
Duplex Stainless steel 22Cr (DSS) is one of the corrosion resistant alloys (CRA) that is used extensively in oil and gas industry for critical applications such as wet gas production flow lines and pipelines. A number of new sour oil & gas projects in the company with high salinity (exceeding 200000 ppm NaCl) will be developed in the coming years. So far 22Cr DSS material is qualified up to 10 mbar partial pressure of H2S (ppH2S) in 160,000ppm chloride levels. The operating conditions of these new projects are outside these current material operating limits of 22Cr DSS defined within the company standards. The objective of the study was to enable wider use of 22Cr grades in higher sour projects in high chloride environments and qualify as lower cost alternative to more expensive CRA materials like 25Cr super duplex, alloy 825 or alloy 625. Pitting, crevice and stress corrosion cracking (SCC) and sulphide stress corrosion cracking (SSC) tests were conducted on both parent material and representative welds in high ppH2S and in high chloride environments using four-point bend test method (FPBT). The results established the new threshold sour service limits of DSS material which resulted in significant cost savings for various projects. This paper will present the test results and discuss the opportunities for 22Cr DSS application.
