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CABLE-TOOL DRILLING

Colonel Drake and Uncle Billy used a steam-powered cable-tool rig to drill the Oil Creek
site. Early drillers in California and other parts of the world also used cable-tool rigs. To understand
the principle of cable-tool drilling, picture a child's seesaw. Put a child on each end of it and let
them rock it up and down. This rocking motion demonstrates the principle of cable-tool drilling. To
explore it further, take the kids off the seesaw and go to one end of it. Tie a cable to the end and let
the cable dangle straight down to the ground. Next, attach a heavy chisel with a sharp point to the
dangling end of the cable. Adjust the cable's length so that when you hold the end of the seesaw all
the way up, the chisel point hangs a short distance above the ground. Finally, let go of the seesaw.
Releasing the seesaw lets the heavy chisel hit hard enough to punch a hole in the ground. Pick up
the seesaw and repeat the process. Repeated rocking of the seesaw makes the chisel drill a hole. The
process is quite effective. A heavy, sharp-pointed chisel can force its way through a great deal of
rock with every blow.
A cable-tool rig worked much like a seesaw. Of course, cable-tool rigs had more parts and,
instead of a seesaw, a cable tool had a powered walking beam mounted in a derrick. At Drake's rig,
a 6-horsepower (4.5-watt) steamboat engine powered the walking beam. The walking beam was a
wooden bar that rocked up and down on a central pivot, much like a seesaw. The derrick provided a
space to raise the cable and pull the long drilling tools out of the hole. As the beam rocked up it
raised the cable and attached chisel, or bit. Then, when the walking beam rocked down, heavy
weights, sinker bars, above the bit provided weight to ram it into the ground. The bit punched its
way into the rock. Repeated lifting and dropping made the bit drill. Special equipment played out
the cable as the hole deepened.
Cable-tool drilling worked very well in the hard-rock formations such as those in eastern
U.S., the Midwest, and California. 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 screwing
together several joints of pipe, they put the bit on the bottom of the hole. As the hole deepens, they
add joints of pipe.
Rotating Systems

With the bit on bottom, the rig can rotate it in one of three ways. Many rigs use a machine
called a "rotary table," a sort of heavy-duty turntable. Others rotate the bit with a top drive, a device

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