Re: Pipe loads on the cheap

Earl Tuson

Tim O' asks,

What is the typical diameter of drill pipe?
Any given well could use a range of pipe sizes.

There are actually two kinds of "pipe" involved, casing and drill pipe. You start out drilling a big hole, with a bit on the bottom of the pipe that is smaller in diameter than the hole you are drilling. Drilling fluids are pumped down through the pipe, cooling the bit and keeping pressure on the formations being drilled through. You can only go so far, or the well could begin collapsing, so you pull out, and insert casing. Casing is a larger pipe. Next, a smaller bit is selected that will fit down inside the casing placed, and drilling commences again. The inital hole size is dependent upon how deep you plan to eventually drill, which is in turn dependent on the particular formation. The largest bit I have knowledge of was a 22 1/2", but the common drill sizes are 12 1/4", 10 5/8", 8 1/2", and 6 1/2". There are additional sizes above and below that as well. I cannot recall the pipe thread sizes on the bottom of the bits, so cannot tell you what sizes the drill pipe is, but I think we only used two thread sizes on the drill sizes I listed above. Casing OD would be a bit smaller than the bit, so it could be shoved into place and then cemented on the outside. ID has to fit the next drill size. So, if you wanted to deliver a load of casing and pipe to a job and haul it all in one freight car load, half has to be one or two sizes of small drill pipe, and half has to be roughly equally divided into several sizes of larger casing.

Both the drill pipe and casing are threaded, and require protective caps during shipment. Nowadays those are plastic (bright blue, red, and so forth,) but I don't know what was used during the steam era.

Earl Tuson
former oil field drill bit engineer

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