Hydraulic motor

A hydraulic motor, comprising:

• (a) a top sub for connecting to a tubing string, a main barrel and a bottom bit sub;
• (b) an impeller housing connected to the top sub and disposed within the main barrel, the impeller housing defining:
• (i) at least one inlet port for directing fluid, received from an intake plenum, into an impeller chamber, and in a direction substantially transverse to a longitudinal axis of the motor, and (ii) at least one exhaust port for exhausting fluid from the impeller chamber into an annular exhaust plenum, wherein outside of the impeller chamber the at least one inlet port is fluidically isolated from the at least one exhaust port;
• (c) an impeller disposed within the impeller chamber and comprising a longitudinal impeller shaft and a hub bearing a plurality of outwardly extending impeller vanes which are positionally and orientationally fixed relative to the hub, wherein fluid directed onto the impeller through the at least one inlet port causes rotation of the impeller;
• and
• (d) a bottom bearing assembly for supporting an adapter shaft disposed within the bit sub;
• wherein the motor defines a fluid path through the top sub, through the impeller housing and an annular space within the main barrel, and which exits through the adapter shaft and the bit sub, and
• a gap exists between a distal outward end of one or more impeller vanes, and an inner surface of the impeller housing.