There are three phases of a Wellbore: drilling, casing, and tubing
Production of oil or gas is a complex, time- and cost-intensive undertaking, but in principle, every wellbore goes through three phases: Drilling with drill pipes, lining with casing pipe and production with tubing. 1. Drilling with drill pipes Drill pipes are durable steel pipes that conduct the force to the drill bit. In many cases the drill pipe turns the drill bit, which cuts into the rock until it reaches the deposits. The last drill pipes before the drill bit are often nonmagnetic drill collars, particularly in horizontal drilling. Drilling with drill pipe is the first phase of every wellbore. Drilling mud meanwhile cools the drill bit and carries the rock cuttings, i.e. the cut rock, back to the surface. 2. Lining with casing The outer tubes are called casing. Casing lines the wellbore and thus protects the layers of soil and above all the groundwater from being contaminated by the drilling mud and/or frac fluids. It also stabilizes the wellbore, so casing must be able to withst...