A pumpjack (also called oil horse, oil jack, donkey pumper, nodding donkey, pumping unit, horsehead pump, rocking horse, beam pump, dinosaur, grasshopper pump, Big Texan, thirsty bird, cricket, oil derrick, or jack pump) is the overground drive for a reciprocating piston pump in an oil well.

It is used to mechanically lift liquid out of the well if not enough bottom hole pressure exists for the liquid to flow all the way to the surface. The arrangement is commonly used for onshore wells producing little oil. Pumpjacks are common in oil-rich areas.

External:

• Wikipedia - Pumpjack