Abstract: The present invention relates to systems and methods for controlling downhole motors and drilling systems incorporating such systems and methods. One aspect of the invention provides a downhole drilling system including: a downhole motor, a transmission coupled to the downhole motor, and a drill bit coupled to the transmission. Another aspect of the invention provides a method of drilling a borehole in a subsurface formation including the steps of: providing a drill string including a downhole motor, a transmission coupled to the downhole motor, and a drill bit coupled to the transmission; and rotating the drill string while flowing a fluid through the drill string to the downhole motor, thereby powering the downhole motor, thereby rotating the transmission and the drill bit.

Abstract: A drilling assembly in an elongated hole including a housing defining an interior with a plurality of motor stages in the interior. Each motor stage has at least one blade with supporting platform surfaces. A casing within the interior surrounds the plurality of motor stages and defines an annular flowpath with the housing. The casing also defines at least one offtake passage adjacent each motor stage. A shielding fluid passes through the annular flowpath and, in turn, the at least one offtake of each motor stage to coat and protect the at least one blade and supporting platform surfaces. A driving fluid passes through the casing for propelling the at least one blade of each motor stage. Preferably, the shielding fluid is at a relatively higher pressure than the driving fluid with a substantially constant ratio maintained between the between the shielding fluid and the driving fluid.

Abstract: A turbine for use in a downhole drill string including an elongated casing defining an interior and a plurality of motor units in the interior. Each motor unit has a rotor and a stator. A torque transmission couplings connects each of the plurality of motor units to the drill string. The torque transmission couplings having flexible linkages. As a result, the power section has tight tolerances for the clearance at the tips of the rotors because the motor units are relatively stiff. The flexing normally obtained by bending the rotor shaft is accomplished and absorbed in the flexible linkages.

Abstract: A drilling assembly in an elongated hole including a housing defining an interior with a plurality of motor stages in the interior. Each motor stage has at least one blade with supporting platform surfaces. A casing within the interior surrounds the plurality of motor stages and defines an annular flowpath with the housing. The casing also defines at least one offtake passage adjacent each motor stage. A shielding fluid passes through the annular flowpath and, in turn, the at least one offtake of each motor stage to coat and protect the at least one blade and supporting platform surfaces. A driving fluid passes through the casing for propelling the at least one blade of each motor stage. Preferably, the shielding fluid is at a relatively higher pressure than the driving fluid with a substantially constant ratio maintained between the between the shielding fluid and the driving fluid.

Abstract: The present invention relates to a seal arrangement in which a substantially labyrinth type seal is utilised between a rotating component and a stationary component such as a housing. An edged fin of the seal arrangement incorporates a slot nozzle or a slot nozzle is associated with a fin in order that fluid flow through those slot nozzles either impinges upon opposed surfaces or at least narrows the available leakage gap width for greater sealing efficiency. Typically, several seal arrangements in accordance with the present invention and possibly in association with simple barrier fins are combined in an assembly to provide an appropriate acceptable combined operational sealing efficiency in a turbine engine.