system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When something falls into a drilling hole on an oil rig, why is it so catastrophic and expensive to fix? What goes into fixing it?
gpt
Drilling into the ground for oil or gas is expensive. If, during a bit change or other time there is an open hole, a piece of metal falls in, it can damage the tri-cone or hammer bits used to do the drilling. The carbide buttons on the bits do the work, and are very hard, but brittle. Metal in the hole can snap these and slow or halt the drilling process. A bit can cost around $2000 per inch of the diameter of the bit. Sometimes, the bits can fail if the bearings go out, due to too much weight put on them, or from a manufacturers defect. The entire drill stem needs to then be "tripped" back out of the hole, to gain access for what is called a "fishing trip", where magnetic ended, barbed, or other means of grabbing what fell in or fell off back up out of the hole. At any time, there are 2-4 large diesel engines running on a rig, to drill, pump fluids, or to compress air for drilling purposes, which can use around 55 gallons or more of fuel per hour. That fuel cost, plus cost of the 3-5 man crew, the waste of time for the setback, the possibility of a downhole pipe casing cementing crew being on location and on hold due to unforseen problems like an idiot dropping a pipe wrench down the hole when breaking apart a flange on the casing and leaving it in a precarious spot...wait time and fishing trips can cost hundreds of thousands of dollars in added expense.