STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

904 Drilling and Well Completions
of the swivel. As mentioned previously, the tool has to be pulled out when
adding a single.
Figure 4-217 shows the same operation using a side-entry sub. With this sub,
the electric wireline crosses over from inside the drill pipe to the outside.
Consequently, singles may be added without pulling the steering tool out. On
the other hand, there is a risk of damaging the cable if it is crushed between
the drillpipe tool joints and the surface casing. The wireline also goes through the
rotary table and special care must be taken not to crush it between the rotary
table and the slips. Furthermore, in case of BHA sticking, the steering tool
has to be fished out by breaking and grabbing the electric wireline inside
the drillpipes.
Figure 4-218 shows the arrangement of the sensors used in a steering tool.
Three flux-gate-type magnetometers and three accelerometers are positioned
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and Use S; Kelly
,
Drum , for Cable
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Cable left loose
- Steering Tool Probe
Figure 4-217. Typical operation of a steering tool for orienting the drill bit
using a side-entry sub. (Courtesy SPE [loll.)