The magnesium ion, present in formation and injection waters in downhole conditions in the oil and gas production industry, is a key determinant in CaCO3 scale formation. In the work reported herein, the kinetics of calcium carbonate scale formation is studied both in the bulk solution and on the metal surface and the comparisons are given. Mg is shown to have a greater inhibition effect on precipitate formed in the bulk solution than scale formed on the metal surface.

The effect of the Mg ion on the scale formed on the metal surface was studied systematically in this paper, which includes the kinetics, morphology, and Mg/Ca ratio of the deposit on the metal surface. The Mg ion incorporates into the deposit crystals and the ratio of Mg in the deposits formed on the metal surface is proportional to the ratio of Mg/Ca in the scaling water. Simultaneously, the Mg ion accelerates the crystal transformation from vaterite to calcite and adsorbs on the surface of vaterite and calcite causing the increase in the surface roughness in addition to distortion of crystals. To link the effect of Mg ions on the kinetics, morphology of scale formed on the metal and Mg/Ca ratio of the deposit on the metal surface, it is shown that Mg incorporates into the deposited crystals and poisons the growth sites of the crystals, which inhibits the growth rate of deposit formed on the metal surface.

Subject
Scale morphologies, Ions, Precipitation (solids), Metal surfaces, Vaterite, Scale inhibitors, Carbonate scales, Calcite, Bulk solution, Crystal growth, Scale formation, Scale, Magnesium
Keywords:
magnesium, scale, calcium carbonate
© 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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