A downhole tool for use in a downhole drill string is provided. The downhole tool includes a rotor movably coupled within a stator, and a drive shaft movably coupled within a bearing housing. The drive shaft has a first end coupled with the rotor and a second end coupled with a drill bit. Bearing assemblies interfaces engagement between the drive shaft and the bearing housing, including polycrystalline diamond elements, each with an engagement surface, and an opposing engagement surface of a non-superhard metal.

A drill string steering system includes a motor and a rotary valve body disposed in a tool body. The motor includes a motor shaft coupled to the motor and extending within a central bore of the tool body. The motor shaft has a downhole engagement portion that includes a first splined surface. The rotary valve body includes a disk-shaped component and a valve shaft coupled to the disk-shaped component and extending uphole of the disk-shaped component. The valve shaft includes a second splined surface engageable with the first splined surface for rotation of the motor shaft to be imparted to the rotary valve body.

A drill string steering system includes a motor and a rotary valve body disposed in a tool body. The motor includes a motor shaft coupled to the motor and extending within a central bore of the tool body. The motor shaft has a downhole engagement portion that includes a first splined surface. The rotary valve body includes a disk-shaped component and a valve shaft coupled to the disk-shaped component and extending uphole of the disk-shaped component. The valve shaft includes a second splined surface engageable with the first splined surface for rotation of the motor shaft to be imparted to the rotary valve body.

A bearing assembly having independently rotatable concentric inner and outer tubes. A bearing chamber containing multiple bearings is disposed between the tubes, allowing thrust but not rotation to be transferred between them. The bearing chamber is sealed from the inside of the inner tube. To prevent high pressure fluid from leaking from the inner tube to an exterior of the tool through the bearing chamber, damaging components, a flow path is formed. An annular piston responds to high pressure within the bearing chamber and the inner tube, opening a flow path from the inner tube to the environment.

A downhole tool includes a housing and a housing chamber. The housing chamber is separated from a fluid chamber by a seal. The seal maintains a pressure differential between the housing chamber and the fluid chamber. A pressure adjuster between the housing chamber and the fluid chamber maintains the pressure differential below a maximum pressure differential.

A radial bearing apparatus including a housing with a housing bore defining a radial bearing housing surface, a shaft extending through the housing bore and defining a radial bearing shaft surface, and a radial bearing contact interface between the radial bearing housing surface and the radial bearing shaft surface for bearing a variable side force applied to the shaft. The radial bearing contact interface includes an oblique section in which the radial bearing housing surface and the radial bearing shaft surface are oblique to each other when the side force is zero and progressively increase in contact in an axial direction in response to an increasing magnitude of the side force.

A downhole tool for use in a downhole drill string is provided. The downhole tool includes a rotor movably coupled within a stator, and a drive shaft movably coupled within a bearing housing. The drive shaft has a first end coupled with the rotor and a second end coupled with a drill bit. Bearing assemblies interfaces engagement between the drive shaft and the bearing housing, including polycrystalline diamond elements, each with an engagement surface, and an opposing engagement surface of a non-superhard metal.

Bearing assemblies, apparatuses, systems, and methods include bearing assemblies where one of the bearing assemblies may include bearing surfaces defining an at least partially conical inner surface.

A tool for building a wellbore includes a tool body with a flow passage extending axially therethrough, a piston chamber formed radially through the tool body that intersects the flow passage of the tool body, a piston disposed in the piston chamber, at least one actuation element that exerts a force between the piston and the piston chamber, and a sleeve disposed within the flow passage of the tool body that includes at least one cutout. When the sleeve is in a first position within the tool body, the cutout is axially offset from the piston, and when the sleeve is in a second position, the cutout is axially aligned with the piston.

A downhole drilling motor assembly includes a first motor, a second motor aligned coaxially with the first motor, and a clutch assembly aligned coaxially with the first and second motors. The clutch assembly independently and selectively actuates each of the first and second motors to rotationally drive a drill bit. A related method includes: mounting a drill bit at a distal end of a drill string at a well site; and providing a downhole drilling motor assembly which rotationally drives the drill bit. The clutch assembly is controlled to independently and selectively actuate the first and second motors, and the drill bit is rotationally driven via the independent and selective actuation of the first and second motors.