Because many reservoirs lack sufficient pressure to produce fluids to the surface, the majority of the world's oil and gas wells require the assistance of artificial lift (AL) systems, which use a variety of methods to supply the energy needed to help bring fluids from reservoir to surface.
Numerous AL options are available. Engineers choose systems based on surface conditions, reservoir characteristics, production properties, fluid types and operational considerations. Electrical submersible pumps (ESPs) are often chosen for their versatility. ESPs comprise a series of centrifugal pump stages contained within a protective housing.
Beam pumps use sucker rods to lift fluids and are the most common form of AL because they are simple, easily maintained, and relatively inexpensive. Progressing cavity pumps (PCPs) lift fluids when a rotator within the pump stator is turned by sucker rods that are connected to a surface motor. Although limited to lower production rates than some AL systems, PCPs are often chosen for their ability to process solids-laden fluids.
Plunger lift systems, the simplest and least expensive form of AL, consist of a piston that pushes fluids to the surface. The piston is intermittently carried upward through the tubing by gas pressure beneath it after the piston falls to the bottom of the tubing string.
Hydraulic pumps inject high-pressure fluid down one tubing string, to force formation fluids to the surface through a second tubing string. Plunger lift systems are frequently used for heavy oil applications. Gas lift systems aid flow to the surface by reducing the density of formation fluids in the wellbore, which allows available reservoir pressure to push the fluids to the surface.
An Oilfield Review Defining Series article “Artificial Lift” focuses on the basics of AL systems and the design considerations engineers use in their selection and application.
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