An apparatus uses at least one injection pump (9) positioned in proximity to an undersea petroleum well (10) to provide hydraulic fluid for hydraulic pumping equipment positioned in the bottom of the well, in order to cause a flow of produced oil. The injection pump (9) is able to suction hydraulic fluid from a tank of hydraulic fluid (8) positioned on the deck of a service unit (40). Alternatively, injection pump (9) is able to utilize water from the sea as a hydraulic fluid. Alternatively, the injection pump (9) may be integral with a Christmas tree manifold (6) or may be installed in an auxiliary well (90) in order that it's external portion does not enter into contact with seawater.