Artificial lift for oil or gas wells is used to boost production rates. Energy is added to the well to lower the bottomhole flowing pressure and increase the suction on the reservoir rock (“drawdown”).
This energy source is usually electricity which is used either to drive pumps (sucker rod, progressive cavity or electric submersible) or gas compressors (gas lift). The higher the energy applied, the higher the reservoir drawdown and hence the well flow rate.
Artificial lift methods are usually classified as follows:
The earliest used artificial lift methods were displacement pumps which derived from equipment used to pump water (e.g. windmills, Archimedes screw). The most common displacement pump used in the global oilfield is the sucker rod or beam pump (shown). These pump liquids at relatively low rates, i.e. 50 to 500 barrels per day (bpd).
For higher flowrates (up to 20,000 bpd or higher), electric submersible pumps (ESPs) are installed in the wellbore with a high power cable to supply electricity to the motor.
Aside from pumps, the other most common method is called “gas-lift” where high pressure gas (usually 1000 to 2000 psig; 70 to 140 barg) is injected into the tubing deep in the wellbore. This lightens the fluid mixture (reduces the density) which in turn reduces the bottomhole pressure which creates more reservoir drawdown and therefore flow.