Importance

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Abstract

A downhole drilling motor, e.g. a turbodrill, which is connected to a string of drill pipe has a rotating shaft for driving a drill bit which may be a rotary bit or a high speed solid head diamond bit. The turbine section has rotor and stator blades which are crescent shaped in cross section for maximum turbine efficiency. The drilling motor may alternatively be a positive displacement motor. The bearing shaft is provided with suitable rotary seals positioned below the rotary bearings carrying both radial and vertical thrust. Fluid lubricant fills the space from the rotary seals to a predetermined level above the bearings. A piston seals the lubricant chamber and is pressurized by drilling fluid (i.e. mud) flowing through the tool. The bearing shaft, which conducts drilling mud from the turbine section and exhausts the same at the drill bit, is provided with a radially extending passage which communicates with a labyrinth seal positioned below the lower rotary seal. This passage and labyrinth seal is operable to leak drilling mud past the lower rotary seal to maintain a fluid pressure on the lower seal that is substantially the same as that on the upper rotary seal, thus balancing the pressure on both of the bearing seals to provide substantially extended life thereof.

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First Claim