Corrosion and Wear Indicators for Wirelines

Armor wire brittleness:

• Rule of thumb - the user should be able to perform a "wrap" test, by bending a wire around a rod twice its own diameter 5 times without the wire cracking or breaking. More specifically, wire brittleness is moat critical at the point where the cable is terminated at the cable head. Cased hole termination of the wires normally involves bending them around a small radius before trimming. The wires should be able to bend around this radius without cracking or breaking.
  

• Another common location which is affected by wire brittleness is at the top of the cablehead where the wireline enters the head. A "gooseneck" or other device designed to provide support of the wireline around the recommended bend radius at the cable head, should always be utilized when lifting the tool string. A visual inspection of this area of the wireline after every run is recommended, particularly if the wireline has tested brittle.

Abrasive wear:

• Physical wear on the outer wires due to abrasion of the cable against the wellbore, formations or casing. Uniform wear around the outside of the cable is less suspect than wear on one side of the cable in a particular section. Individual wires with less than 90% of the original diameter will exhibit only 80% of the original break strength.
  

• In the case of localized wear, a careful observation of the entire length of wireline would be necessary. Polished sections in a used wireline would indicate localized wear on high wires or larger diameters, this interval should be inspected more carefully.

Corrosive wear:

• Corrosives or chemical attack can cause localized pitting in the wires. The "wrap" test can again be utilized as a ductility indicator for the individual wires.
  

• General corrosion can occur in a cable which is exposed to a corrosive fluid the last run in the well and then not ran for a period of time. The critical time frame is dependent upon several factors, i.e. - type of corrosives, amount of lubrication in the wireline, etc.
  

• This type of exposure can also cause severe localized corrosion on the outer wraps of wireline at the lowest point on the drum. Corrosion is usually most pronounced on the inner armor wires. When inspecting for this type of corrosion, the inner and outer wires would need to be tested for brittleness every 6" for an interval equal to the circumference of the drum on the outer surface of the wireline. If brittleness is detected in any of these individual tests, then this procedure should continue until all unacceptable brittleness is removed.

Miscellaneous damage:

• Physical operational damage such as kinks, nicks or flat spots should be removed from the operating cable if a service repair center cannot restore the wireline to its original condition.

An evaluation should be made about the usefulness of the wireline considering all of the above factors. Evaluation of a wirelines previous operating or handling history, brittleness, corrosion, or uneven/excessive wear is critical to performing a successful job.

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