Well drilling tool with lubricant level indicator

Abstract

A turbo drill 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 cresent shaped in cross section with each blade having an exit angle of 14.degree. - 23.degree. for maximum turbine efficiency. 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 predetermine 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. A plug member in the bearing shaft is positioned to be dislodged at the low lubricant position of the first piston to provide a temporary obstruction to the flow of drilling fluid to give an indication, at the well surface, of loss of lubricant in the turbo drill. An optional feature provides for increasing the pressure drop of drilling fluid in the turbo drill 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. A further optional feature is a locking ring arrangement which prevents separation of threaded connections in the drill housing during use.