A pumpjack is the device that uses a reciprocating rod to pump oil from a well.
Its walking-beam mechanism moves a sucker rod up and down inside the well. The rod operates a downhole pump that lifts oil to the surface when underground pressure is no longer sufficient for natural flow.
The familiar surface structure is powered by an electric motor or an internal-combustion engine. Counterweights help balance the beam and reduce the energy needed for each stroke. Pumpjacks are common on mature onshore oil fields.
A pumpjack is not the same as a drilling derrick, which supports equipment during well construction. It is also different from a wellhead or Christmas tree, the assembly of valves and fittings that controls production at the surface. Some wells use other artificial-lift systems, including gas lift and electric submersible pumps.