|
Under
certain conditions the natural chemistry of produced fluid
derived from the reservoir geology can lead to the formation
of salts, which in turn can deposit as scale in the production
system. Similarly, deposition can be promoted when seawater
is either injected into the reservoir (to maintain pressure)
or has migrated to the producing zone from another zone. Certain
scale deposits can also arise when the reservoir has turned
sour due to increased microbial activity. All of these scenarios
can lead to severe scale deposition problems when the pressure
and temperature in the production and processing plant changes.
The major types of scale, along with treatment strategies
are listed below:
- Calcium Carbonate
Calcium carbonate usually originates from the nature of
the reservoir itself or has been stimulated by the co-mingling
of produced fluids from two or more different producing
zones or reservoirs. This scale is normally formed when
there is a decrease in pressure, releasing carbon dioxide
and changing the pH. The main mitigation strategies are
dissolution by acidification or application of calcium
carbonate scale inhibitor.
- Barium Sulphate
In general barium sulphate scale results from water incompatibility,
primarily from either seawater injection and / or seawater
breakthrough, co mingling with produced water rich in
barium. Barium sulphate is highly insoluble and will deposit
at temperature drops across the production processing
plant. Mitigation strategies include the removal of sulphate
ions from seawater for re-injection, application of barium
sulphate scale inhibitors or treatment with specialist
dissolvers.
- Iron Sulphide
Iron Sulphide scale is deposited where microbial enhanced
corrosion has become a serious problem. The scale is derived
from the reaction of iron oxide from corrosion and hydrogen
sulphide, a by-product of sulphate reducing bacteria metabolism.
Treatment for iron sulphide is application of a specialist
chelating and dissolution agent followed by microbial
control with biocide application.
- Calcium Sulphate
Calcium Sulphate scale is relatively soluble and only
poses a real problem when conditions are close to the
solubility limit and super-saturation occurs.
- Sodium Chloride
Sodium Chloride scale is caused by a saturation and evaporation
process and is readily removed by warm water in most cases.
Roemex
can supply a wide range of both scale inhibition and scale
dissolving chemicals. Roemex prefer to carry out in-house
laboratory testing, which includes
jar tests and dynamic scale loop testing to develop a product
specific to a clients operational requirements.
|
Scale
Inhibitors 
