In oil and gas production erosion corrosion at components with reduced flow diameters, like gravel packs, nozzles, and Christmas trees. is causing serious problems. Production rates are often limited by critical fluid velocities which in most cases are unknown. Those critical fluid velocities (erosion corrosion breakaway velocities) are reported rarely in literature especially for highly alloyed materials. Reasons are on the one hand that determination of such velocities is experimentally highly sophisticated when avoiding destruction of the testing facility. On the other hand, conventional erosion corrosion testing facilities (rotating cylinders, discs, etc.) supply in many cases poorly defined conditions especially with respect to flow velocity. Most erosion corrosion tests are therefore done at low flow velocities below 10 m/s which do not sufficiently attack corrosion resistant alloys.

A combined flow loop - jet impingement pilot plant has been established to determine mass loss rates in a mixed gas - saltwater - sand multiphase flow at velocities up to 70 m/s. Investigated materials were those applied in oil- and gas fields (various stainless steel grades).

Conditions of an Austrian gas condensate well have been investigated using a gas-liquid-ratio of 1x103 and 3x103. As liquid phase an artificial brine with a salt content of 27 g/l was used. Sand content with grain size below 200 μm was up to 80 times higher than field conditions to accelerate testing. CO2 with a partial pressure of 15 bar was used as gas phase.

Fluid flow velocities and particle distribution have been calculated by multiphase computational fluid dynamics in the impingement cell. Verification of these data was done with particle image velocimetry. Mass loss rates have been determined with optical profilometry after a testing time of 72 and 94 h. Damaged surfaces were investigated by SEM.

Critical flow velocities of investigated materials are presented and effects of chemical composition and mechanical properties are critically discussed.

Subject
Test methods, Steel surfaces, Materials, Sand, Impingement, Mass loss, Nozzles, Flow velocity, Impact velocity, Steel, Brines, Stainless steel, Erosion corrosion
Keywords:
erosion corrosion, multiphase flow, flow loop, jet impingement, critical flow velocity
© 2007 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).
2007
Association for Materials Protection and Performance (AMPP)
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