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Indeed, a few cable-tool rigs are probably drilling wells somewhere in
the world even now, although their use peaked in the 1920s and faded
thereafter. In spite of cable-tool drilling's widespread use in the early
days, the system had a couple of drawbacks. One was that cable-tool
drillers had to periodically stop drilling and pull the bit from the hole.
They then had to run a special basket, a bailer, into the hole to retrieve
and remove the pieces of rock, or cuttings, the bit made. After bailing
the cuttings, they then ran the bit back to bottom to resume drilling. If
the crew failed to bail out the cuttings, the cuttings obstructed the bit's
progress. Bailing cuttings was not a big hindrance, however, because
the cable-tool system allowed the crew to do it quickly. Since the
cable was wound onto a winch, or windlass, called the "bullwheel",
the crew simply reeled cable on and off the bullwheel to raise and
lower the bit and bailer. Reeling cable was a fast operation.
A far bigger problem than bailing, and the one that led to
cable-tool drilling's demise, was that the cable-tool technique didn't
work in soft formations like clay or loose sand. Clay and sand closed
around the bit and wedged it in the hole. This limitation led to the
increased use of rotary rigs because more wells were being drilled in
places like Spindletop where cable-tool bits got stuck. The wall cake
created by circulating drilling fluid prevented formations from
collapsing.

ROTARY DRILLING
Rotary drilling is quite different from cable-tool drilling. For
one thing, a rotary rig uses a bit that isn't anything like a cable-tool's
chisel bit. Instead of a chisel, a rotary bit has rows of teeth or other
types of cutting devices that penetrate the formation and then scrape
or gouge out pieces of it as the rig system rotates the bit. Further, a
rotary rig doesn't use cable to suspend the bit in the hole. Rotary crew
members attach the bit to the end of a long string of hollow pipe. By

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