There is an increasing demand for high strength (more than 110 ksi grade) tubing that is applicable at high temperatures between 175 and 200°C for XHPHT (Extreme High Pressure and High Temperature) wells in mildly sour environments. Super 13Cr stainless steels categorized as "13-5-2" in ISO13680 are typically used in HPHT wells containing CO2 with and without small amount of H2S. However, the temperature limit of super 13Cr stainless steels is equal to or less than 175 °C. In this study, the effect of alloying elements of stainless steels on general corrosion resistance at high temperature and environmentally assisted cracking resistance at the high temperatures and room temperature was investigated. It is found that Cr, Ni, Cu and Mo are effective elements for improving resistance to general corrosion and cracking at the high temperatures and room temperature in CO2 environment with and without small amount of H2S. From the results, new stainless steel, super 17Cr stainless steel with 125 ksi grade has been developed. The new steel shows good cracking resistance in both the typical gas and severe oil well conditions in 0.001 MPa H2S + 3 MPa CO2 environments at 200 °C. Furthermore, the no Sulfide Stress Cracking (SSC) region of super 17Cr stainless steel - 125 widens in lower pH direction compared with that of super 13Cr stainless steel with 110 ksi grade.

Subject
Environmental cracking, Materials, Sodium chloride, Corrosion cracking, Cracking resistance, Corrosion products, Sodium chloride solution, Steel, Pitting, Corrosion resistance, Stainless steel, Sulfide stress cracking, Stress corrosion cracking
Keywords:
OCTG, stainless steel, environmentally assisted cracking, SSC, SCC, H2S, CO2, XHPHT well, high strength, super 17Cr stainless steel
© 2012 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2012
Association for Materials Protection and Performance (AMPP)
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