Page 333 - Drilling Technology in Nontechnical Language

324 Drilling Technology in Nontechnical Language Second Edition

Washover and basket tools

Within this class of tool there are three types: the fishing magnet, tools
that use fluid movement to catch small bits of junk, and tools that use a

barrel to go over bits of junk and then close below the junk.

A fishing magnet can be either a permanent magnet run on drillpipe
or it can be an electromagnet run on wireline. Fishing magnets are useful
only for small pieces of ferrous junk.

Tools that use fluid movement include the jet junk retriever (fig. 13–8).

With the tool at the bottom of the hole, a ball is dropped that diverts flow

around the outside of the tool and back up inside the end. Spring-loaded
fingers allow small bits of junk (such as a drillbit cone) to enter the end of

the barrel and are held in place by the fingers closing below the junk.

Fig. 13–8. Jet junk retriever

In general, tools that use a barrel to go over the fish are called washover

tools.
Washover tools are available with a milling shoe on the bottom (which
can cut some rock at the bottom as well as mill on junk) and with spring-
loaded catch fingers inside. This is used to go over the junk and to catch it

inside the barrel.

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