A testing campaign has been performed to assess the applicability of the modified 13% Cr martensitic stainless steels as tubing material for the production wells of Smørbukk and Smørbukk South fields on the Åsgard area of the North Sea. Due to the well conditions, mainly the high temperatures (up to 165°C), the high concentrations of chlorides (up to 68 g/l) and the H2S partial pressure (1.8 kPa), sulphide stress cracking and localised corrosion resistance were the main concerns. The design requirements for the specified minimum yield strength of the tubing material were 95 ksi (655 MPa) and 110 ksi (758 MPa). Eight steels from three different manufacturers with different chemical compositions have been tested. To assess their SSC resistance constant load, four-point bent-beam and C-ring tests have been performed at room temperature. Furthermore, to assess the localised corrosion resistance of the material pitting and crevice tests were performed at the highest temperature expected in service. The results of the tests have made possible to decide the applicable materials. Grade 95 ksi and 105 ksi steels showed very good resistance to SSC and only one of the 110 ksi grade materials failed. The localised corrosion test results showed that the testing conditions were at the limit of the steel resistance.

Subject
Constant load, Test methods, Water, Materials, Autoclaves, Condensed water, Crevices, C ring stress corrosion testing, Steel, Pitting, Corrosion resistance, Localized corrosion, Sulfide stress cracking
Keywords:
sulphide stress cracking, crevice, pitting, modified 13% Cr, sour gas/oil wells, tubing, testing
© 1997 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).
1997
Association for Materials Protection and Performance (AMPP)
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