Everybody knows that oil wells and derricks go together. The tall
derrick towers are needed to hoist drilling equipment in and out of the
hole.
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When men start to drill a well, they fasten a cutting tool, called a
bit, to a piece of pipe which hangs upright in the derrick. Machinery
turns the whole thing round and round, so that the bit grinds down into
the earth. When one length of pipe, called a joint, has almost
disappeared into the hole, men screw another joint onto the top of it.
Now the engine turns the double-length pipe, and the bit digs down
deeper.
Men, working on the floor and high up in the derrick, hoist more and
more joints into position and screw them together as the bit goes on
down. After a while, the bit gets dull. A new one must be put on. So,
strong cables that run over wheels at the top of the derrick begin
lifting the whole string of pipe out. Joint by joint, they unscrew the
pipe and stack it out of the way. When the last joint comes up, men
change the bit. Then back the pipe goes, joint after joint, into the
hole.
Wells must often be drilled more than two miles deep before the bit
breaks through into an underground reservoir of oil. That means that the
string of drilling pipe must be two miles long. The machines that help
to handle it are very strong, but on many rigs, men have to use their
own muscles a great deal, too.
For deep drilling, the most modern rigs have a lot of fine new
machinery. Automatic tongs take a tight grip on the drilling pipe when
it is being unscrewed. Men used to work the tongs by hand. Mechanical
hands
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now keep the bottom joints from dropping back into the hole, and arms
high up in the derrick do the job of stacking the pipe.
The skillful men who work with the pipes and the machinery call
themselves roughnecks. The driller is the one who actually controls the
drilling pipe. He never says he is digging a well. He says he is “making
hole.”
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Almost all deep wells are now drilled by the turning pipe and bit, which
are called a rotary rig. But sometimes you can see an old-fashioned
cable rig at work. It makes hole with a bit that pounds its way down
into earth and rock. A cable raises the bit, and then lets it fall down
with a bang that chips away a hole. On both kinds of rig, the hole is
cleaned out with water. The water turns the rock dust into mud, which is
then pumped out.
The cable rig idea is about two thousand years old! That long ago
Chinese drillers made water wells, salt wells and even oil wells. The
picture shows what one of these ancient rigs was like.
Look first of all at the long board attached to the rope that goes up
over a roller and down into the well. Then look at the platform behind
the board. Men jumped from this platform down onto the board. That
jerked on the rope and pulled the drilling bit up in the well hole. When
a man jumped off the board, the bit fell down and chipped away some
rock. Round and round a whole crew of men raced, jumping onto the board
and climbing back onto the platform as fast as they could. Still it took
a long time to drill a well--sometimes as long as ten years.
[Illustration]
Now look at the big wheel turned by a bull at the right. This wheel
lifted the pipe made of hollow bamboo that you see at the left. The
pipe was actually a bailer. Every once in a while the men poured water
into the hole, let the bailer down and hauled up mud. Then the bit could
go on drilling. Oil workers today still call the wheel which winds up
cable “the bull wheel.”