Methods and apparatus for pumping fluids from a well utilizing a submersible pumping system. In one embodiment, the pump comprises a pump body operable to be disposed within tubing within a well. The pump body encloses a pump chamber having an inlet and an outlet. The inlet is in fluid communication with the well. A diaphragm is disposed within the pump chamber and forms a boundary between the pump chamber and a diaphragm chamber. A piston is moveably disposed within the diaphragm chamber. The piston may be moved within the diaphragm chamber by a pressure intensifier supplied with a pressure differential from the surface.