Oil and gas production handbook - Process Control and ...

Antifoam
Polyelectrolyte
Methanol (MEG)
TEG
separation in reasonable time. An emulsion breaker is added
to prevent formation of, and break down of the emulsion
layer by causing the droplets to merge and grow. Sand and
particles will normally be carried out by the water and be
extracted in water treatment. However, the emulsion can
trap these particles and sink to the bottom as a viscous
sludge that is difficult to remove during operation.
The sloshing motion inside a separator will cause foaming.
The foam will cover the fluid surface and prevent gas to
escape. Also, the foam reduces the gas space inside the
separator, and worst case it will pass the demister and
escape to the gas outlet as mist and liquid drops. An
antifoam agent is introduced upstream of the separator to
prevent or break down foam formation, by reducing liquid
surface tension.
Polyelectrolyte is added before the hydrocyclones and
causes oil droplets to merge. Works by reducing surface
tension and water polarity. This is also called flocculation
and polyelectrolyte flocculants and allows emissions to
reach 40 ppm or less.
Methanol or Mono Ethylene Glycol (MEG) is injected in
flowlines to prevent Hydrate formation and prevent
corrosion. Hydrates are crystalline compounds that form in
water crystalline structures as a function of composition,
temperature and pressure. Hydrates form and freeze to
hydrate ice that may damage equipment and pipelines.
For normal risers, hydrates form only when production stops
and the temperature start to drop. Hydrate formation can be
prevented by depressurization which adds to startup time or
by Methanoli injection.
On longer flowlines in cold seawater or arctic climates,
hydrates may form under normal operating conditions and
require continuous methanol injection. In this case the
methanol can be separated and recycled.
Hydrate prediction model software can be used to determine
when there is a risk for hydrate formation and to reduce
methanol injection or delay depressurization.
Tri Ethylene Glycol (TEG) is used to dry gas. See scrubbers
and reboilers chapter.
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