Nah, there’s no plate tectonics involved in that particular case. It’s all on the North American plate. Not a whole lot of folding either.
It’s literally just sedimentation and time.
That particular well (the one involved with the Deepwater Horizon) is part of the Mississippi River system. The river carries a lot of sediment along the way and dumps it in the ocean. While this is a continuous process, it happens a bit more after the spring floods. There have been literally millions of years’ worth of sediments constantly dumped in the Gulf of Mexico. That eventually works out to sediment thicknesses of several miles.
Add in some salt from when the region was a near landlocked ocean that evaporated away. And some organic matter to generate oil, and Bob’s your uncle. There is some trickiness for the temperatures and pressures that allow oil to generate instead of getting over or undercooked and in the local geology to provide adequate traps so the hydrocarbons don’t just float off, but those conditions seem to have been met in this case.
Of course, this starts at 1550m elevation, so it might not be the deepest mine (measured from Earth’s core)
Even the ultimate borehole, the Kola Superdeep Borehole , got less than a third of the way through the crust at a depth of 12200m (starting at about 230m, so 12km down). The crust thereabouts is only about 35km thick, so it was still less than 1/3rd of the way through.
But yes, we have barely scratched the top 1/10th of the Earth’s crust, and the whole of the crust (average 100km deep but varies greatly) is only about the top 1.5% of the Earth.
If you want to reach the core you need to go a lot,lot,lot deeper.
Weird things happen when you go that deep. When you climb a mountain, the ambient air pressure drops to below that of sea level; but when you go down in a mine, the ambient air pressure increases to above that of sea level. When you go down to 2500m below sea level (4 km below the 1550m mine entrance level), the ambient pressure is 19.7 psi. When you get that far, the rock is hot, just from geothermal heat; in that mine, the rock is reportedly at around 150F. If you think you can cool it by blowing air down the main shaft, think again. When you compress air, it heats up (this is why diesel engines work). So when you force 70F air from 1500m above sea level down to a depth where it’s at 19.7 psi, the temperature increases to…surprise, about 143F. You won’t get any cooling effect at all. According to the Wikipedia page, cooling is instead achieved by pumping ice slurry down from the surface.
Another fun occupational hazard is rock burst. the rock at that depth is under crazy high pressure from all sides. That is, until miners arrive and relieve the pressure on one side. At that point, the exposed rock can literally explode outward toward the miners - in some cases, killing them. Here is a series of very small rock bursts in a tunnel, just big enough to take your eye out. Now imagine one that fires hundreds (or thousands) of pounds of rock at you. :eek:
Given the large difference between equatorial radius and polar radius: 3,963 miles (6,378 kilometers) vs 3,950 miles (6,356 km) or 13 miles (22 km) less. I don’t think standing at the North Pole qualifies as being extremely deep just because you’re closer to the core than just about any underground site.
If you just want to get down as deep as you can, check out the Soudan Mine in northern Minnesota. A really cool old iron mine converted to a state park. It will get you down to 713m. It takes a long time to get that deep. Cool stuff if you are interested.