Sulfate-reducing bacteria (SRB) pose a threat to oilfield produced water facilities due to microbiologically influenced corrosion and biogenic sulfides. Produced water systems are susceptible to the establishment of oil-coated SRB-enriched biofilms that are typically inaccessible to conventional biocide regimes. To address this, a strategy has been designed using a conventional biocide in combination with anthraquinone (AQ), a non-toxic compound that specifically inhibits the SRB sulfate-reduction pathway.[1,2] AQ is applied as submicron colloidal particles that penetrate oil-coated biofilms and are taken up by SRB cells. The combination treatment has enabled successful control of biogenic sulfides in water injection systems due to a synergistic action on sessile SRB.[3,4] In the present study, AQ and a tetrakishydroxymethyl phosphonium sulfate blend (THPSBLEND) were used to treat slop water tanks on a Floating, Production, Storage and Offloading Unit (FPSO) operated by Petrobras in the Campos Basin, offshore from Brazil. High levels of hydrogen sulfide (≥ 30 ppm in the water) were being generated by aggressive SRB present in the tanks, resulting in safety, economic, and discharge issues. Conventional treatment with glutaraldehyde was ineffective. The AQ-THPSBLEND co-treatment immediately reduced and maintained hydrogen sulfide levels at <1 ppm. During the course of treatment, the amount of AQ applied was increased and THPSBLEND decreased, which resulted in a stable, cost-effective scenario for bacterial control that enabled safe discharge of the water into the marine environment due to low ecotoxicity. This finding is significant in that it provides an economically favorable protocol to mitigate biogenic sulfides in oilfield water tanks and vessels and minimizes personnel and environmental risk during treatment and discharge.

Subject
Costs, Water, Hydrogen concentration, Optimization, Biofilms, Produced water, Ports and harbors, Floating production storage and offloading units, Sulfides, THPS, Biocides, Risk reduction, Oil
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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