It seems like to me that the drill pipe would flex and other problems would arise due to being in a liquid rather than solid soil or rock.
I guess they know how to do this but do they have to use a lot different equipment than they use to drill on land?
Huh? The bottom of the ocean is soil and rock as well.
But you have a mile-long length of drill shaft that is basically unsupported. I wonder about this too.
The drill pipe has to pass through 5000 feet of water before it hits the bottom of the ocean - that’s what I mean. Ocean water has currents for 1 thing that can push the pipe around. The water does not just sit there.
Here is a pretty good explanation of the different types of offshore rigs. It would seem that the drill is not necessarily lowered down 5000 feet from the surface, but from a substructure some ways down into the water.
Nice link DC, I especially liked the diagram showing the different types of drill rigs in different depth waters.
Here is a link to specifications for the Deepwater Horizon rig, saying it was a semi-submersible rig. The riser is the portion that Bijou is talking about; it would have to be designed to handle the currents and other forces (such as bending) underwater.
One thing you have to appreciate is that the drillstring is under tension. The drill bit is pushed into the rock by the weight of the drill collars, very heavy section steel tubes just above the bit, and the collars are hanging off the drillstring. Nothing is pushing down from the top.
That said, there’s a huge amount of the mechanics of drilling that I don’t know or don’t understand. If there’s any drillers or rig engineers on the Boards, feel free to open an “Ask the…” thread.