Qualification of seamless X60QOS and X65QOS linepipe grades for extreme sour service conditions with partial pressure of H2S beyond 1 bar

Seamless X60QOS and X65QOS linepipes are widely used for Sour Service offshore and onshore applications. Sour Service refers to the risk of hydrogen related cracking, such as by Sulfide Stress Cracking (SSC). The International standard NACE MR0175 / ISO 15156 provides requirements for assessing the resistance to SSC, specifically on how to qualify for use in region 3 of the environmental severity diagram (Figure 1 in paragraph of part 2). Qualification requires exposing materials in an acid solution saturated by 1 bar of H2S (NACE TM0177 Solution A) and to apply a tensile stress above 80% AYS by means of different methods: uniaxial tensile, C-ring or Four-Point Bend. However, for very sour fields presenting H2S partial pressures much greater than 1 bar, the preservation of the SSC resistance might be questioned and is presently a major concern for the O&G industry. 

Product Number: 51320-14585-SG
Author: Florian Thebault, Laurent Ladeuille, Laurent Lamps, Harold Evin
Publication Date: 2020