Bronze and metal monument honoring the cable tool driller, located in downtown Artesia Wells, New Mexico
Percussion drilling is simply the constant dropping of heavy tools to dig a hole into the ground, pretty much allowing gravity to do Her thing. You may think of it like using a bar to dig a post hole. For the well to be as close to vertical as possible, and there to be no drag as the down hole bit assembly moves up and down, in and out, it is vitally important to spud the well as vertically straight as possible.
Great care was taken to drive the initial conductor pipe with the use of hand levels and plum bobs. Subsequent strings of protective casing set as the well became deeper and deeper were as also set as vertical as possible thus avoiding drag, obstructions and allowing the bottom of the bit to hit flat in the hole, every strike. I found it odd to find so many old photographs of casing strings set to string lines nailed to the rig floor, until I sorted it all out.
That subject, however, is left for another day.
We're on to a cable tool rig component called a temper screw.
Petrolearn Definition - What does Temper Screw mean?
Temper Screw is a drilling feed device which is used in an oil rig during the drilling process to help in feeding and slightly turning the drill jar at each stroke. It is a screw link on which the rope of a rope drilling apparatus is attached. These screws are used for adjusting the drilling apparatus. It is also known as a set screw.
Above is a big temper screw, the driller with his hand on the screw to feel what he's drilling. The screw is a bit like a break on a conventional wireline draw works that allows you to regulate weight on the bit.
I suspect like all things in the oilfield being the cable tool screw man, required a great deal of talent and years of experience. You were, after all, the driller. You could tell what it was you were drilling, shale, limestone or sand, had to keep your holes as straight as possible, your bits as sharp as long as possible, and not get any of that stuck downhole.
Getting percussion tools stuck downhole was so common, mechanical "jars" were placed in the bottom hole assembly as early as the 1870's. You could pick up and drop the jars that in turn transferred energy to the BHA and help free
Drillers were always busy, watching over the entire rig and all the hands. There were logs that also had to be kept, all of which was hand written, in pen and ink, or pencil, including the nature of the rock or shale being drilled, rates of penetration, what was in each bailer run every time the hole was cleaned out, and oil odors, sheens in the hole fluids, etc.
Drillers also sat on their asses a lot, as this fella, above, is doing. He has a neat stool that he can stand on to adjust the temper screw, then sit down and watch the banging going on. The driller on the left has the same sort of stool.
In the late 1890s and early 1900's, particularly in sandstones along the Texas and Louisiana Gulf Coasts, rotary tables were used more than cable tools and for several decades there was a terrible rift between cable tool hands and rotary rig hands, one gang quite certain their way was better.
A nice photo of North Texas in 1929 by Basil Clemmons. A string of casing is set in the well and the hands are all probably WOC. The temper screw is pulled back and hung off in the derrick.
We'll talk about the half-oval track looking thing laying on the rig floor; it was very common back in the day, a precursor to a cat head, if you will, and and saved cable tool hands lots of hard work.
This is a pretty cool little video of a real life, steam driven cable tool rig in operation at a museum somewhere; maybe even the terrific Permian Petroleum Museum between Midland and Odessa. Under the derrick is the well bore, the walking beam picks up, and drops, the bit and bottom hole assembly downhole. The temper screw is clearly visible.