51312-01552-Effect of Micro Alloying Elements on Sour Service Grades with Higher Strength

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Product Number: 51312-01552-SG

ISBN: 01552 2012 CP

Author: Luca Moderer

Publication Date: 2012

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Production of hydrocarbons of CO2/H2S containing reservoirs is nowadays required. Increasing CO2/H2S contents cause a decreasing pH-value. For deep reservoirs high strength steels need to be used. Casing and tubing out of higher strength materials lead to a pronounced material saving due to reduced wall thickness. Those requirements will be fulfilled on the one hand by high sour gas resistance of steel qualities and on the other hand by demands on mechanical properties of steel qualities. This is also shown in the draft of API Specification 5CT where a C110 API grade is included. Therefore investigations with various contents of micro alloying elements Nb V Ti and B were performed. Different alloys in lab scale with approximately 130 kg were melted and afterwards rolled. Constant load and fracture mechanical testing was done to evaluate SSC resistance according to NACE Standard TM0177-2005 Method A and D. The specimens were tested in solution A (5 wt% NaCl 05 wt% CH3COOH) with 100 % H2S concentration at 1 bar. Scanning microprobe and EF-TEM studies were performed for further characterization of microstructure and segregations of materials. Different contents of micro alloying elements resulted in different SSC resistance. Effects are critically discussed.