A pumping system for a heavy oil and sand slurry from a downhole location to the ground surface includes a conventional screw type pump having a rotor and stator. At the bottom of the stator at the inlet thereto is mounted an attachment including a sleeve having a number of slots in the side surface...http://www.google.fr/patents/US5015162?utm_source=gb-gplus-shareBrevet US5015162 - Attachment for an oil well screw pump system
