Sulphide Stress Cracking (SSC) Resistance of 13% Cr and Super 13% Cr Stainless Steels below pH 3.5 In Low H2S Environment

The use of martensitic SS is limited to H₂S partial pressure of 0.1 bar for pH values above 3.5. However, martensitic SS have been successfully used in Field A up to 0.015 bar of H2S at pH 3. It is decided to qualify these steels for Field B and Field C for H2S partial pressure up to 0.04 bar at pH 3. The SSC tests were duplicated in two independent laboratories. In one of the laboratories, test samples are placed in both liquid phase and gas phase under condensing conditions. In parallel, H₂S concentration variations along the top part of the tubing during shut in conditions were measured in some wells. The paper summarises SSC and SCC results on martensitic and super-martensitic stainless steels under the conditions of Field B and Field C, in liquid and gas phases, and evaluates the SSC severity in shut in conditions considering the H₂S evolution in gas wells. The tests confirm the suitability of these steels up to 0.04 bar of H₂S at pH 3 -3.2. Possible reasons for the successful use of 13% Cr in the field A are summarised.