Real-Life Math
You're drilling for oil. The geologist tells
you that at 3,500 feet there should be an oil formation. She wants a core
sample from that depth.
How do you know when to change to a core bit?
A core bit is a drill bit that will gather core samples.
That's
simple, according to drilling instructor Doug Gibson: you count the joints
that you've added to your drill.
OK, he says, maybe it isn't
that simple. Gibson explains that not all drill joints are the same length,
though they average around 31.5 feet. In addition, he says that in the confusion
of excited drilling, it's easy to lose count of the number of joints
a crew has added.
"Drillers have to know exactly what's in the
hole," said Gibson. "It seems simple: just addition. But when things are going
fast, they [the drilling crew] might be adding a link [a joint] every 10 minutes."
Gibson
says if you're unsure how many joints you've added, there's
a simple way to calculate it. "Every good crew knows exactly how many pipes
[joints] they have at their location," he said. "If you think you lost track,
you count what is there and subtract that from what you started with."
The
worst has happened and you think you lost count of the drill joints you added
while you were drilling.
If you started with 150 joints at your location
and someone counts the remaining ones and tells you 83 are unused, how many
joints will you probably need to add before you change to a core bit?