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6. Pigs & Darts for Coiled Tubing
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Introduction:
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We often have general enquiries from customers on pigs and darts, so first
we provide an overall view and guidance on the range of possibilities. We
have quite an extensive range, as can be seen from the subsequent listings.
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Nomenclature:
There are two broad classes.
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Class 1 refers to the scraper, wiper and foam types (and we do not mind whether you call
them pigs, darts or plugs). These are usually used for the at-surface cleaning, in
a variety of ways, of tubing, rather than sent down-hole, though there can be
exceptions. These, in larger sizes, are also used in tubes and pipes and also
in non-oil applications.
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Class 2 refers to the cement, shearable, acid and solid darts, which are used
in down-hole operation to control the passage of cement (or occasionally acids
or other fluids) into the well bore for operations such as blocking off
water-producing perforations.
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Class 1 types are relatively simple and cheap, and are usually available
ex stock. Class 2 are more complex to design and produce as they consist of
a burst disc welded into a steel body, over-moulded with rubber. Cement darts are
quite often tailored for the individual well (for 2-3/8" tubing and bigger, they
always are) and in any case need to be carefully selected to be appropriate.
They are therefore not as cheap, and are mostly produced to requirement.
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