To enhance asset capacity utilization and operational flexibility, produced water (PW) and sea water (SW) were comingled for several years as part of water flooding large Alaskan oil fields. Comingling led to severe corrosion and the functional loss of several pipelines. Detailed investigations revealed that inorganic scale, solids, low velocities, lack of supplemental corrosion inhibition, maintenance pigging ineffectiveness, and bacteria were principal factors that resulted in the lack of adequate corrosion control. A rigorous management of change process and aggressive corrosion mitigation efforts were implemented to separate PW and SW. Lessons learned from the above experiences were also applied to temporary PW-SW comingling efforts necessitated by business/operational constraints as well as emergency situations leading to inadvertent mixing of PW and SW. A mitigation matrix was developed and successfully implemented as an asset integrity management tool in addressing risks of PW and SW mixing temporarily or under emergency conditions. A set of key performance indicators specific to monitoring the effectiveness of mitigation measures were also implemented.

Subject
Pits, Water, Corrosion rate, Slopes, Solids, Inspection, Corrosion scales, Corrosion inhibitors, Mixing, Water injection, Pigging, Infrastructure, Maintenance
Keywords:
produced water, sea water, comingle, mitigation, pigging
© 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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