Descaling

Scaling can be caused by many issues in the oil and gas sector but in simple terms it occurs when dissolved salt ions found in produced water are exposed to a change such as pressure or temperature and during mixing with other produced water streams/seawater which contain other dissolved salt ions that are incompatible with them which, once mixed, create a new insoluble salt which then drops out as scale.

Depending upon the amounts of scale formed this can lead to a restriction in flow or even a blockage.

SANCCUS SOLUTIONS

The scale formed will depend upon the type of dissolved salts present and which incompatible salts they are mixed with;

1. Calcium ion + sulphate ion = calcium sulphate (sulphate type scale)
2. Calcium ion + carbonate ion = calcium carbonate (carbonate type scale)

The resulting scale formed will determine which type of chemical product is needed to treat it and hence the treatment method

Carbonate type

Carbonate type scales are easily treated with an acid based product as they are readily solubilised in this type of product which is fast acting. However, they can also be treated with an alkali based chelating product. This is especially useful if there are other materials present in the scale mix that are acid insoluble or are other materials present in the scaled up system that can be damaged by acid treatment.

Sulphate type

Sulphate type scales are not soluble in acid based products so need to be treated with alkaline based chelating products. These target the low solubility ions and effectively bind and remove them from the water allowing more to solubilise etc. This type of product typically needs to be used at temperature 50-90°C to work in a time effective manner but will still work at lower temperatures. However, treatment times will be longer.

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