Schlumberger

Radioactive Marker Sub

The radioactive marker sub is run in line with the workstring above the packer. It serves as a tubing collar or drillpipe tool joint, with one or two small cavities drilled and threaded to receive a sealing plug. A radioactive pip tag is installed in each cavity. A pip tag is a weak gamma ray source (1 -µCi of cobalt-60). All radioactive material is fully recovered when the string is pulled.

Accurate gun depth positioning

A through-tubing gamma ray log is used for depth correlation of the pip tag with the earlier openhole gamma ray log. Because the distance from the pip tag to the top shot was measured previously, the gun can be accurately positioned on depth.

Specifications
Size and rating Matches the corresponding tubing or drillpipe thread connection
Half-life Cobalt-60: 5.2 years
Optional zinc-65: 240 days
Radiation level (mrem/hr at 1 ft) 1-µCi pip tag: 0.014

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Radioactive Marker SubRadioactive Marker Sub
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