Double shaft drilling apparatus with hanger bearings

A drilling apparatus comprising:

• a housing defining a longitudinal axis and a nominal internal diameter, the housing including a relatively narrow section that exhibits a limited internal diameter that is less than the nominal internal diameter;
• a payload bay disposed adjacent relatively narrow section of the housing;
• a torsion rod disposed in the relatively narrow section of the housing, the torsion rod supported to rotate concentrically about the longitudinal axis, the torsion rod including a relatively narrow midsection positioned in substantial alignment with the relatively narrow section of the housing;
• a power section including a rotor, wherein the rotor is adapted to move with eccentric rotary motion with respect to the longitudinal axis in response to the passage of drilling fluids through the power section;
• a power transmission shaft interconnected between the rotor and the torsion rod, wherein an upper end of the power transmission shaft is movable with the eccentric rotary motion of the rotor, and wherein a lower end of the power transmission shaft is movable with the concentric motion of the torsion rod;
• and
• a mandrel for supporting a drill bit coupled to and driven by the torsion rod, the mandrel coupled to the torsion rod by at least one flexible coupling, the mandrel disposed at an oblique angle with respect to the longitudinal axis.

A method of operating a drilling apparatus, the method comprising the steps of:

• providing a power section including a rotor, wherein the rotor is adapted to move with eccentric rotary motion with respect to a longitudinal axis in response to the passage of drilling fluids through the power section;
• providing a power transmission shaft having an upper end coupled to the rotor and movable with the eccentric rotary motion of the rotor and a lower end constrained to move with concentric rotary motion with respect to the longitudinal axis;
• providing a torsion bar coupled to the lower end of the power transmission shaft and movable with the concentric rotary motion of the lower end of the power transmission shaft;
• providing a mandrel coupled to the torsion bar by at least one flexible coupling, the mandrel disposed at an oblique angle with respect to the longitudinal axis, the mandrel rotatable in response to rotation of the torsion bar;
• and
• passing a drilling fluid through the power section to move the rotor, thereby inducing eccentric rotary motion of the upper end of the power transmission shaft, concentric rotary motion of the lower end of the power transmission shaft, concentric rotary motion of the torsion bar, and rotation of the mandrel.