Environmental cracking of high strength casing in mud has been experienced but its mechanism has not been clarified. Degradation of lignate mud with time and its effects on steel in the mud were experimentally investigated in a laboratory. Sulfide concentration of mud increases and pH value of mud decreases with aging time. In an aged mud, hydrogen absorption and cracking of steel were observed when pH of the mud was lowered. Sulfide which was formed from mud change into H2S by a decrease in pH which was caused by dissolution of CO2. CO2 was observed to form from mud. As the result, sulfide stress cracking occurs, which is a proposed mechanism of cracking of casing in mud.

Subject
Environmental cracking, Materials, Hydrogen permeation, Hydrogen concentration, Hydrogen content, Hydrogen absorption, Drilling fluid, Acidity, Bubbling, Steel, Sulfide stress cracking, Stress corrosion cracking, Aging
Keywords:
High Strength Steel, High Strength Casing, Mud, Hydrogen Embrittlement, Environmental Cracking, Sulfide Stress Cracking
© 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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