Drilling rigs can drill for oil up to 40,000 feet below the earth's surface. Rig equipment rotates a string of pipe with a diamond-tipped bit that can drill through soil and rock. While drilling, fluid is pumped into the well bore to maintain pressure and prevent fluid or gas from prematurely entering the well. At pre-determined depths, the rig stops and installs a casing pipe to prevent the well bore from caving in. When the well reaches the hydrocarbon reservoir, equipment is installed inside the well and at the surface to maintain pressure and prevent blow-outs.