Definition - What does Air Drilling mean?
Air Drilling is a process in which gasses, mostly nitrogen or compressed air are used to cool a drill bit. The gasses are used instead of liquids to lift cuttings out of the wellbore. This drilling process is more advantageous as compared to drilling with liquids as it is much faster and may exclude lost circulation problems. There are five types of Air Drilling based on the conditions of the drilling site. The conditions involve the presence of a borehole fluid-influxes or oil-based mud. It is also known as pneumatic percussion drilling.
Petropedia explains Air Drilling
As air is an ideal low-density drilling intermediate, Air Drilling procedure has many advantages. This drilling technique is preferred due to its increased penetration rate, low cost, super control in cavernous, extended bit life and lost circulation areas. It also provides minimal harm to the liquid sensitive zones.
For this technique, water-bearing formations are the biggest problems, as it is not defined how much formation water-influx rate can be handled. Air Drilling disadvantages include sloughing of the formation, soft formations and possible downhole fires and explosions. These disadvantages are responsible for the reduction of its efficiency.