When a well is first drilled, the reservoir is usually under enough pressure to push fluids all the way up the wellbore and into surface facilities — this is called natural flow. As a field is depleted, that pressure falls, fluid columns get heavier with water, and eventually the reservoir can no longer overcome the weight of the fluid in the tubing. At that point production stops unless extra lifting energy is supplied. Artificial lift supplies that energy.
More than 60% of producing wells worldwide rely on some form of artificial lift, and roughly 90% of all oil wells require it at some point during their producing life.
Why wells need artificial lift
A vertical column of fluid in the wellbore exerts hydrostatic pressure that the reservoir must overcome to deliver flow to surface. Several things conspire to defeat natural flow over time:
- Declining reservoir pressure — the dominant driver of energy out of the rock falls as hydrocarbons are removed.
- Rising water cut — produced water is denser than oil, making the fluid column heavier to lift.
- Lower gas energy — dissolved gas that once helped lift fluids comes out of solution and is depleted.
Artificial lift can also be installed from day one on wells that never flow naturally, such as many heavy-oil and unconventional shale wells.
The main types of artificial lift
Operators choose a lift method based on fluid volume, depth, gas content, viscosity, sand, and cost. The four most common families are:
A surface beam unit drives a sucker-rod string to operate a downhole positive-displacement pump. Best for lower-volume, oil-rich wells.
A multistage centrifugal pump runs downhole on an electric cable. Best for high fluid volumes.
Gas is injected into the wellbore to lighten the fluid column so reservoir pressure can lift it. Good for high gas-oil-ratio wells.
A helical rotor turns inside a rubber stator. Excels with high-viscosity heavy oil and fluids carrying solids.
Each method has a sweet spot, and many fields use a combination across their well population. See the artificial lift comparison for a side-by-side breakdown.
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Frequently asked
A well needs artificial lift when reservoir pressure can no longer push fluids to surface — typically as pressure declines, water cut rises, and the fluid column becomes too heavy to flow naturally. Some wells, such as heavy-oil and many shale wells, require lift from the very start.
The sucker-rod pump (the familiar pumpjack) is the most widely deployed lift method by well count, especially on lower-volume onshore oil wells. ESPs handle the largest fluid volumes, and gas lift is common offshore and on high gas-oil-ratio wells.
More than 60% of producing wells worldwide use artificial lift, and around 90% of oil wells need it at some stage of their life as natural pressure declines.