Acid systems are commonly used to improve productivity through either near-wellbore (NWB) damage removal or through dissolving scale inside the wellbore during production. This paper describes a methodology for qualification of the acid system’s material compatibility adopted by an operator on the Norwegian continental shelf.

As part of the acid treatment qualification, corrosion is a key parameter that should be addressed carefully, particularly for high temperature wells. This paper discusses the following two acid qualification programs:

  • Case 1: API(1) 5CT grade 13% Cr-80 and UNS(2) S41426 martensitic stainless steel well construction materials and a reservoir temperature of 135°C

  • Case 2: API 5CT grade 13% Cr-80 tubing material and a reservoir temperature below 100°C

For Case 1, the challenge was to qualify an acid system; while, for Case 2, the objective was to optimize the acid formula. Static corrosion tests were conducted and general corrosion rates were determined by weight loss measurements, while microscopic analysis was performed to evaluate the presence of localized corrosion.

The qualification approach presented describes a stringent methodology for qualification of acid systems used for scale removal or acid stimulation treatments to help prevent severe corrosion of the well construction materials.

Subject
Acids, Materials, Corrosion rate, Materials performance, Corrosion testing, Magnification, Organic acids, Pumping, Fluids, Corrosion inhibitors, Pitting, Construction, Alloys
Keywords:
Acid treatment, Corrosion, API 5CT grade 13% Cr-80, UNS S41426 martensitic stainless steel
© 2017 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).
2017
Association for Materials Protection and Performance (AMPP)
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