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.
------------------------------
Paul Tibbals
------------------------------
Original Message:
Sent: 08-10-2020 06:42
From: Waleed Khalifa
Subject: Corrosion in multiphase flowlines
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…
------------------------------
Waleed Khalifa
president
Arabic Consultancy Center for Engineering Materials, Inspection
Maadi, Cairo
01098163293
------------------------------