Load-bearing universal joint with self-energizing seals for a rotary steerable drilling tool

A rotary steerable drilling tool adapted to be disposed within a wellbore, the rotary steerable drilling tool comprising:

• a collar defining an interior surface and a first longitudinal axis;
• a shaft extending within the collar, the shaft defining an exterior surface and a second longitudinal axis;
• a universal joint adapted to transfer rotation from the collar to the shaft when the collar is rotated;
• a convex surface connected to the shaft and extending circumferentially thereabout;
• a first concave surface extending circumferentially about the shaft, the first concave surface adapted to mate with the convex surface to carry a first axial load applied to the shaft in a first direction;
• wherein the first axial load is applied to the shaft when the first and second longitudinal axes are spaced in either an oblique relation or a parallel relation;
• wherein the rotary steerable drilling tool further comprises a spacer ring disposed within the collar, the spacer ring comprising:
• a second concave surface extending circumferentially about the shaft and adapted to mate with the convex surface to carry a second axial load applied to the shaft in a second direction, which is opposite the first direction;
• wherein the second axial load is applied to the shaft when the first and second longitudinal axes are spaced in either an oblique relation or a parallel relation;
• wherein the rotary steerable drilling tool further comprises:
• an internal shoulder formed into the interior surface of the collar;
• and
• a lock-nut threadably engaged with the collar, the lock-nut extending circumferentially about the shaft;
• and
• wherein the lock-nut compresses the spacer ring against the internal shoulder, thereby applying a pre-load to the spacer ring.

A rotary steerable drilling tool adapted to be disposed within a wellbore, the rotary steerable drilling tool comprising:

• a collar defining a first longitudinal axis;
• a shaft extending within the collar and defining a second longitudinal axis;
• a universal joint adapted to transfer rotation from the collar to the shaft and to carry axial loads applied to the shaft;
• first and second shoulders between which the universal joint is positioned;
• and
• first and second self-energizing seals adapted to seal the universal joint, the first and second self-energizing seals being disposed within the collar and extending circumferentially about the shaft, and the first and second self-energizing seals being located on opposite sides of the universal joint;
• wherein the first self-energizing seal is adapted to be seated against the first shoulder by applying a first pressure differential across a first extrusion gap, the first extrusion gap being defined between the first shoulder and the shaft;
• wherein the second self-energizing seal is adapted to be seated against the second shoulder by applying a second pressure differential across a second extrusion gap, the second extrusion gap being defined between the second shoulder and the shaft;
• and
• wherein the first and second self-energizing seals are adapted to seal the universal joint while the collar is rotated and the first and second longitudinal axes are spaced in either an oblique relation or a parallel relation.

A rotary steerable drilling tool adapted to be disposed within a wellbore, the rotary steerable drilling tool comprising:

• a collar defining a first longitudinal axis;
• a shaft extending within the collar and defining a second longitudinal axis;
• a universal joint adapted to transfer rotation from the collar to the shaft and to carry axial loads applied to the shaft;
• and
• first and second seals adapted to seal the universal joint, the first and second seals being disposed within the collar and extending circumferentially about the shaft, and the first and second seals being located on opposite sides of the universal joint;
• wherein the collar is rotated while the first and second longitudinal axes are spaced in either an oblique relation or a parallel relation;
• wherein the universal joint comprises:
• a convex surface connected to the shaft and extending circumferentially thereabout;
• a first concave surface extending circumferentially about the shaft, the first concave surface adapted to mate with the convex surface;
• and
• a spacer ring disposed within the collar, the spacer ring defining a second concave surface extending circumferentially about the shaft, the second concave surface being adapted to mate with the convex surface;
• wherein the rotary steerable drilling tool further comprises:
• an internal shoulder formed into the collar;
• and
• a lock-nut extending circumferentially about the shaft and threadably engaged with the collar;
• wherein the spacer ring is compressed between the lock-nut and the internal shoulder;
• wherein the first concave surface is adapted to carry a first axial load applied to the shaft in a first direction;
• and
• wherein the second concave surface is adapted to carry a second axial load applied to the shaft in a second direction, which is opposite the first direction.

A method for sealing a universal joint adapted to transfer rotation from a collar to a shaft that extends within the collar, the method comprising:

• providing the collar, the shaft, the universal joint, and first and second shoulders between which the universal joint is positioned, the collar and the shaft defining first and second longitudinal axes, respectively;
• providing first and second self-energizing seals between the collar and the shaft, the first and second self-energizing seals extending circumferentially about the shaft on opposite sides of the universal joint;
• rotating the collar while the first and second longitudinal axes are spaced in either an oblique relation or a parallel relation, thereby rotating the shaft;
• seating the first self-energizing seal against the first shoulder by applying a first pressure differential across a first extrusion gap, the first extrusion gap being defined between the first shoulder and the shaft;
• and
• seating a second self-energizing seal against the second shoulder by applying a second pressure differential across a second extrusion gap, the second extrusion gap being defined between the second shoulder and the shaft.