I find the whole industry fascinating and wish I had done that MSc in Drilling Engineering 24 years ago when I graduated with my Chemistry degree! The thing I find interesting is having to get the hydrostatic pressure of the drilling mud correct so that overcome formation pressure but without fracturing the formation because the hydrostatic pressure is too high.
To think that formation pressure is in 1000s of psi you can see why well control is important. This video below whilst poor quality is quite mind blowing to watch the drill string being blown out the well like a piece of cotton.
As an idea of the pressures and temperatures that can be involved. I worked on the design of a gas riser ( the pipe from the seabed to the surface) for 780bar (eleven thousand psi) pressure and 200 centigrade flowing temperature. if I recall there were some bits of pipe with a 76mm wall thickness of custom steel (X70+)
One of those jobs where you have to think how you are going to buy the steel and get something made for a product where you might normally just select it from a catalogue.
Seeing as there a bit of interest in this, here's a bit of education:
As a rule of thumb, the pressure you see as you drill down into the earth is governed by the density of salty water, that is around 0.45 psi/ft. So at 10,000 ft the pressure is 4500 psi or 300 atmospheres. This is called normally pressured. Rock strength is typically around 0.7 psi/ft, so to frac rock at 10,000 ft you need to apply a pressure of 7000 psi.
In some parts of the world you get what is called overpressure, this can be due to a number of reasons one of which is rock compaction. As layers of rock build up due to accumulation of sediments, the rocks below compact. This would normally expel water, but if the water is trapped it can lead to pressures in excess of normal. The Macondo well was drilled to over 18,000 ft, if normally pressured that would be 8000 psi, in fact reservoir pressure was over 12,000 psi. This was known about and was not the cause of the disaster, that was more due to a failure to properly cement the casing (pipe lining) in the well.
Macondo well was drilled to over 18,000 ft, if normally pressured that would be 8000 psi, in fact reservoir pressure was over 12,000 psi
So is that what caused the kick?
If everything had gone to plan would that have been a routine event to deal with. Eg, shut the pumps, close the annular preventer and then circle the formation fluids out before pumping denser mud down the string?
Sorry if that's a simplistic explanation.
