How Does It Work? The Pump In every ESP, there are two main sections, the motor, and the pump itself. The majority of ESP's operate on a centrifugal pumping system, and they usual operate in a series. How Does a Centrifugal Pump Work? A centrifugal pump works by having an impeller attached to a shaft. As the shaft spins, so doe the impeller. Fluid enters though the eye of the impeller and the impeller transfers the mechanical work from the shaft into the fluid. It does this by increasing the fluids pressure and kinetic energy (velocity). On the suction side of the pump, water is being displaced which creates a low pressure zone and helps suck more fluid into the pump.The exit casing around the impeller usually grows in size as the fluid reaches the discharge outlet. This is to slow the velocity, which results in a head pressure increase.         http://engineering.myindialist.com/2009/lab-manual-principle-of-working-of-centrifugal-pump/#.VTReaiG6fIU To see how a centrifugal pump works click here. Centrifugal-pump stage flow path http://petrowiki.org/File%3AVol4_Page_633_Image_0001.png How the Pump in an ESP Works: Since centrifugal pumps cannot move air or in our case gas, before the fluid enters the pump it goes through a gas separator. The separator agitates the fluid which cause the entrained gas within the oil to break loose and be moved up hole through the annulus. Once the fluid is free of gas, it moves into a series of centrifugal pumps that are one after the other. As the fluid moves through each individual centrifugal stage, its head pressure is increased until it is eventually high enough to be pumped towards the surface. By having a series of centrifugal pumps, the unit becomes much more efficient and it also improves the longevity of the unit. Since you have many pumps doing a little work rather than one pump doing all the work, things  are much less likely to break. To see an animation of an ESP, click here. An ESP diagram which shows the series of impellers (pumps). http://www.franklin-energy.com/submersible-pumps-motors/pumps/esp-systems-5060-hz.aspx Pump Efficiency Where Q is given in gal/min, TDH is given in ft, and C = 3,960; or Q is given in m3/d, TDH = m, and C = 6,750