A Pumping Unit is an overground drive that is used to reciprocate a piston pump in and out of an oil well. The pump is used to lift oil mechanically, especially if the bottom hole pressure is not high enough to make the oil to flow to the surface. It is basically used on onshore wells which produce little oil in oil-rich areas. The rotary mechanism is converted to the vertical reciprocating motion of the motor so that it drives the pump shaft and results in the desired nodding motion. A pumping unit is also known by a variety of names such as Oil Jack, Oil Jack Pump, Nodding Donkey, Oil Horse, Beam Pump, Jack Pump, Horse-head Pump, etc.
Beningson explains Pumping Unit
Pumping units are important components as they help in the pulling of hydrocarbons from an oil well to the surface. They provide the necessary pressure in the wellbore to pull the hydrocarbons in cases where the bottom hole pressure is not enough to push the hydrocarbons to the surface. When an oil well is newly drilled, it has enough bottom hole pressure which enables the flow of hydrocarbons to the surface of earth because of pressure difference. However, with time the bottom hole pressure decreases and thus, the natural flow of hydrocarbons to the surface also decreases. Thus, in order to maintain the necessary pressure inside a wellbore, a pumping unit or an oil jack pump is deployed which lifts the hydrocarbons mechanically to the earth’s surface. It usually produces 5 to 40 liters of oil in each stroke, which is often the emulsion of the oil. The size of the pump depends on the weight and depth of oil that is to be lifted. If the oil is present very deep in the well, it requires a pump jack with high power.