DOWN HOLE WELL DRILLING TOOL

A down hole well drilling tool, e.g., a turbodrill, which is connected to a string of drill pipe as 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. The bearing shaft is provided with chevron 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. A layer of lubricant fluid overlies the first piston and has a second piston covering said fluid and transmitting pressure from the drilling fluid to the lubricant fluid surrounding the bearings. Means is provided to give an indication, at the well surface, of loss of lubricant in the turbodrill. Means is provided to cause the vertical thrust to be carried on the bottom vertical thrust bearings, after the top vertical thrust bearings are worn, and thus extend the drilling life substantially. Another optional feature provides for balancing the pressure across the bearing seals. This is accomplished in one form of the invention by providing pump means operated by the drilling motor to pump drilling mud away from the bearing seals. In another form of the invention, the flow of drilling fluid is divided into two streams, one of which rotates the drill bit, and the other of which passes through the drill bit. The pressure drop across the drilling motor equals the pressure drop across the drill bit, thus balancing the pressure on the bearing seals.