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Corrosion in multiphase flowlines

  • 1.  Corrosion in multiphase flowlines

    Posted 08-10-2020 08:27
      |   view attached
    Understanding failures and corrosion damages in flowlines containing more than one phase are important in oil, gas and petrochemical industries. One major controlling parameter in these damages is the nature of the fluids: water cut %, level of corrodants, chlorides, CO2, H2S and the similar. Another controlling parameter is the flow rate/regime. By reviewing some of the pertinent literature, it was not clear whether the location of corrosion damage is related by some way to flow regime or not. For example: localized corrosion of carbon/low alloy steel at the oil/water interface, in a two phase system, and its possible mechanism is not clear. I would appreciate if you can share your thoughts in this issue…

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    Waleed Khalifa
    president
    Arabic Consultancy Center for Engineering Materials, Inspection
    Maadi, Cairo
    01098163293
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  • 2.  RE: Corrosion in multiphase flowlines

    Posted 08-11-2020 08:22
    In my experience, flow regime does impact aqueous corrosion in oil and gas.  There are two primary impacts which I am aware of:
    • Some flow regimes inherently result in higher wall shear stress on piping and equipment.  Higher wall shear stress increases the rate of removal of protective corrosion scales (iron sulfide, etc.) resulting in increased rate of corrosion.   We have found wall shear stress to be a more reliable method of tracking corrosion impact than strictly velocity, flow regime, or piping configuration.  
    • Hydrocarbons often inhibit corrosion.  Piping may be "lined" with a protective layer of hydrocarbon depending on the chemistry of the hydrocarbon, the quantity of water vs hydrocarbon, and flow regime.  Water has to have access to the pipe wall in order for it to kick off the electrochemical processes.


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    Clay Brittain
    MOTIVA
    Port Arthur TX
    (843) 997-5632
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  • 3.  RE: Corrosion in multiphase flowlines

    Posted 08-12-2020 07:16
    Clay
    Thank you for sharing your experience..

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    Waleed Khalifa
    president
    Arabic Consultancy Center for Engineering Materials, Inspection
    Maadi, Cairo
    01098163293
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  • 4.  RE: Corrosion in multiphase flowlines

    Posted 08-11-2020 21:53
    My only experience with this is with natural gas pipelines which are or were connected to producing fields.  There is usually water associated with these flows.  Sometimes inhibitors are added to the process stream to try to eliminate corrosion at the water level - it's obviously not really a liquid-liquid interface in this situation.  However in some cases there are well production liquids present that are largely hydrocarbon, so there may be a two-phase situation.  Sulfides or CO2 may partition to the water, changing pH.
    Features such as traps and drains are often added to the line to try to collect liquids and take them out periodically, but sometimes low points can develop that will tend to trap water.  This can occur from earth movement. 
    Internal corrosion along water levels may cause very serious linear (axial) corrosion, leading to pipeline failure.  One such noted failure in 2000 is described various places, but a short summary is available at Catastrophic corrosion of natural gas pipeline (I have no connection to the firm hosting the summary).
    "Pigs" or traveling scrapers may be used to try to remove materials or even deposits.  These are introduced at specific launching stations and likewise recovered downstream.
    Areas that have current or past corrosion are commonly revealed by the corrosion occurring parallel to the pipe at a constant elevation, on both sides of the 6 o'clock position.  The corrosion may be strictly electrochemical but is often enhanced by the action of microbes (Microbiologically Assisted Corrosion).  There is a lot of research out there into characterizing the microbes into classes based on the corrosion and growth environment, and test kits to determine this.  While I have been out of that area for some time there was work being done to characterize microbes present with DNA-style analysis.

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    Paul Tibbals
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  • 5.  RE: Corrosion in multiphase flowlines

    Posted 08-12-2020 07:16
    Paul
    Helpful details. Thank you..

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    Waleed Khalifa
    president
    Arabic Consultancy Center for Engineering Materials, Inspection
    Maadi, Cairo
    01098163293
    ------------------------------



  • 6.  RE: Corrosion in multiphase flowlines

    Posted 08-12-2020 20:18
    Paul Tibbals has provided a good overall summary.  In multi-phase liquid-liquid-gas flow (such as crude oil, free water and associated gas), flow regime can play a large role in corrosion. For example, stratified flow allows water to form a separate phase at the 6 o'clock position of the pipeline which can result in general or local wall loss, leading to leaks and possibly pipeline rupture.  In a gas-liquid pipeline (a wet gas pipeline), corrosion inhibitor may not necessarily reach to 12 o'clock position of the position in stratified flow. If condensation occurs because of temperature drop (as might occur as an above-ground pipeline becomes a subsea pipeline), the top of the line can corrode. Inhibitor-laden liquid droplets do reach the top of the line in slug flow or annular mist flow regimes.  Maintenance pigging can force inhibited liquid to the top of the line.  Some good references to consider are:
    • Corrosion and Asset Integrity Management for Upstream Installations in the Oil and Gas Industry, by Carlos Alberto Palacios Tenreiro
    • A soon-to be published book by NACE Int'l, Corrosion Control in Petroleum Production, 3rd Edition, by Robert J. Franco and Tim Bieri


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    Robert Franco
    mr.corrosion@yahoo.com

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  • 7.  RE: Corrosion in multiphase flowlines

    Posted 08-16-2020 13:56
    Ropert
    Thank you for the reply and the references...

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    Waleed Khalifa
    Principal and CEO
    Arabic Consultancy Center for Engineering Materials, Inspection
    Maadi, Cairo
    01098163293
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