New alloys have been developed that are resistant to the aggressive conditions typically encountered in oil and gas production from deep, hot, sour environments. C-ring and slow strain rate tests (SSRT) were performed to investigate the hydrogen embrittlement resistance and the effect of sulfur on the stress corrosion cracking resistance of several age-hardenable, corrosion-resistant alloys (CRA's). The alloys studied included UNS N07718, N09925, N07048, N07716, N07725, N10276, and R58640. These alloys are often specified for completion equipment for hot, sour wells where highly saline brine and free sulfur are produced along with natural gas containing CO2 and H2S. C-rings of each alloy were stressed to 100% of yield and tested in accordance with NACE TM0177.1  The results of the C-ring tests indicated that all of the CRA's tested were resistant to sulfide stress cracking (SSC). The simulated downhole environment for the SSRT program consisted of 20% NaCl, 75 psi (5.2 bar) hydrogen sulfide (H2S), 700 psi (48.3 bar) carbon dioxide (CO2), with and without 1 g/L elemental sulfur. All SSR tests were conducted at 300°F (149°C). Nearly all of the alloys tested showed some susceptibility to stress corrosion cracking (SCC) in the environment containing free sulfur; only UNS N10276 and UNS R58640 were immune to cracking under the laboratory test conditions. The results indicate that the presence of sulfur increases susceptibility to stress corrosion cracking. In the non-sulfur containing environment, UNS R58640 and the nickel-base alloys with at least 48% nickel and 6% molybdenum were resistant to SCC.

Subject
Sulfur, Strain rate, Materials, Corrosion resistant alloys, C ring stress corrosion testing, Elongation, Elemental sulfur, Deposit corrosion, Risk reduction, Sulfide stress cracking, Alloys, Stress corrosion cracking, Slow strain rate technique
Keywords:
sulfide stress cracking (SSC), stress corrosion cracking (SCC), elemental sulfur, corrosion-resistant alloys (CRA's), completion equipment, slow strain rate test (SSRT)
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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