How does oil drilling work?

Read the article in the source i provided..it has complete explanation that is too long to explain here..How does oil drilling work?
A very basic answer is provided. Oil well drilling involves a drilling rig, drill pipe and a drilling bit. The bit is attached to the end of the drill pipe and the drilling rig turns the drill pipe which turns the bit and drills into the earth. In order to cool the bit and circulate the hole clean of solds as it is drilled, a mixture of chemicals referred to as drilling ';mud'; is pumped down the inside of the drillpipe, out the bit, and around the space between the hole being drilled and the drillpipe. Another very important purpose of the drilling mud is to apply hydrostatic pressure within the wellbore during drilling and prevent oil %26amp; gas from blowing out.





After the well is drilled to some fixed depth (say 1000 feet), the drillpipe and bit are removed from the well while keeping the hole full of drilling mud. Larger diameter pipe referred to as casing is then run into the well and cement is pumped down the casing and around the space between the casing and the hole to displace the drilling mud to the surface where it is captured for reuse. The inside of the casing is flushed clean so as to only leave a small of amount of cement in the very bottom. After the cement has hardened, it is drilled out with a smaller bit and the process above continues for each casing string until th