Page 257 - Drilling Technology in Nontechnical Language

248 Drilling Technology in Nontechnical Language Second Edition

Fig. 10–10. Logging on drillpipe

For more severe conditions where the wellbore through the formations
to be logged cannot be logged conventionally, the tools can be physically
attached to the bottom of the drillpipe. The pipe, with the logging tools
below, is run in the hole for a distance. Wireline is run inside the pipe
with a special connector on the bottom, which latches onto the top of the
logging tools. A special sub, called a side entry sub, is then used to allow
the cable to be run outside the pipe to the surface. Now as the drillpipe and
tools are run in and pulled out, the winch operator can pay out or pull in
the wire to keep the wire in tension.
Coiled tubing was discussed in chapter 5. Logging tools can be attached
to the bottom of coiled tubing, and the electrical wires are run inside the

reel of tubing. Coiled tubing has sufficient rigidity that it can often (though
not always) push through high-angle and problem hole sections to get the
logging tools to the correct depth.

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