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Our water maker is facing a problem while processing the crude oil mixture. The electrostatic plates are reversed because it is not possible to break the emulsion present.

Composition of the crude mixture:
- Mars blend 58%
- Basrah Medium 20%
- Bouri 8%
- Lokele 7%
- Frade 2%
- WTI 2%

Wash water Desalter 4.5%, brine desalter not present.
- DeltaMix valve 0.35 kg/cm2.
- Raw density 845 kg/m3
- watermaker inlet temperature 120°C
- Water OUT desalter pH 8
- IN water sample not present
- Head water pH 8

Feb-2024

Answers

Joan de la Paz, Baker Hughes, joan.paz@bakerhughes.com

Based on the blend composition I'll not expect usually big issues on desalting, then a deep study on this issue will be needed. but some suggestions that may help to improve the desalter operation and/or the brine downstream management:
- Try to reduce the Wash Water pH optimizing the SWS operation (if is the source of the water), removing Tram amines (if any) or apply an acidification program.
- As Bashrah medium is high on solids that can stabilize the emulsion try to pretreat at the tank farm to maximize the solids decantation.
- No information about the demulsifier then an optimization there is recommended.
- If brine arrives with emulsion to the water treatment plant apply a settling aid or a reverse demulsifier.

Mar-2024
Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

Well, checking the datasheet of the crude oils involving the processing blend informed in the question it's possible to note that the feed stream to the desalting system is a mixture of light and sweet crudes with heavy crudes. The light crudes tends to present high paraffins concentration which can lead to chemical instability in mixtures with heavy crudes and then causing asphaltenes precipitation which stabilize emulsions reducing the separation efficiency in the desalter vessels and provoke the change in the brine colour (the question do not provide information regard this). In this case, it's possible to solve the problem applying a crude stabiliser agent which is dosed independently of the emulsion breaker agent which needs to be applied in this case.

It's also important to check if there is no internal damage to desalting systems which can lead to contact between the shell of the desalter and the electrodes. It's important to analyze if the desalting system suffered some instability event which caused internal damages to desalters like the electrodes breaking, for this it's necessary to open the desalters and access the internals of the equipment.

There are very good references about this topic available in the technical literature and a good example is the article published on PTQ Magazine by Mr. Brian Benoit and Mr. Jeffrey Zurlo in 2014 regarding the impacts of North American shale oil processing in the refining chain, which you can VIEW HERE

Feb-2024