Production that uses the pressure of gases present in the wellbore
As production decreases, techniques must be employed to assist the declining pressure, although it is not replacing the pressure
Techniques known as artificial lift
Main form of artificial lift in primary recover is pumps
Electrical Submersible Pumps
(ESPs) Multistage centrifugal pumps that use blades, or impellers, attached to a long shaft. The shaft is connected to an electrical motor that is submerged in the well. The pump usually is installed in the tubing just below the fluid level, and electricity is supplied through a special heavy- duty armored cable.