Patent ID: 6854517

Claim:
A method of pumping a viscous material in a well with a submersible pump assembly comprising the following steps: (a) providing a centrifugal pump with a plurality of impellers, each of the impellers having vanes with an exit angle of greater than 30 degrees, the centrifugal pump comprising a plurality of zones, with each zone comprising a plurality of the impellers and wherein the exit angles of the impellers in each zone decrease from one zone to another in a downstream direction to account for a reduction in viscosity of the viscous fluid as it passes through the centrifugal pump; (b) connecting an electric motor directly to the centrifugal pump for driving the pump; (c) lowering the centrifugal pump and the motor into a viscous fluid in the well having a viscosity of at least 500 centipoise; (d) providing power to the motor to pump the viscous fluid; and (e) causing a decrease in the viscosity of the viscous fluid as it discharges from the impellers.