Nodding donkey

A nodding donkey is the overground drive for a submersible pump in a borehole. A nodding donkey pump is usually driven by an electric motor and “nods” at a regular rhythm. Depending on the size of the submersible pump, it produces between 5-40 litres of oil-water mixture at each stroke. If you have ever seen one; there is a 2 inch wide metal rod that disappears into the ground hundreds or perhaps thousands of feet down into the oil reservoir.