After the well has been perforated, acidized or fractured, the well may not produce by natural flow. In such cases, artificial-lift equipment is usually installed to supplement the formation pressure.

Sucker-Rod Pumps
The artificial-lift method that involves surface pumps is known as rod pumping or beam pumping. Surface equipment used in this method imparts an up-and-down motion to a sucker-rod string that is attached to a piston or plunger pump submerged in the fluid of a well. Most rod-pumping units have the same general operating principles.

Injection Wells
In the ordinary producing operation only a portion of the oil in place is recoverable by primary production methods. Such methods include free-flowing wells and production maintained by pumps. As oil is extracted from a reservoir or sands the pressure which brings the oil to the well is reduced. Secondary recovery methods are intended to increase the recoverable percentage of the oil in place by injecting a substance such as gas or water into the producing formation. The injected substance is intended to increase the pressure on the oil in the formation and drive it toward the well-bore.

A well, called an injection well or water injection well, is usually drilled in order to inject the substance. Sometimes a previously drilled, abandoned well can be reworked as an injection well. When water is used as the injectant it is often produced on the property itself. Excess water produced by operating wells may be diverted to the injection well and used as the injectant. This method of water disposal usually alleviates the need for a separate water disposal well. If the water from the producing wells does not provide enough injectant to provide proper pressure for secondary recovery, a water supply well may be required to provide an adequate supply of water.