Abstract: According to one embodiment of the invention, a rotary steerable tool includes a drive shaft configured to be coupled to a drill string at an upper end thereof and configured to be coupled to a drilling tool at a lower end thereof. A middle portion of the drive shaft is disposed axially between the upper and lower ends and has a smaller diameter than each of the upper and lower ends. The drive shaft further includes a housing rotatably coupled externally to the drive shaft and at least one housing module coupled to a respective opening in the housing at an axial location corresponding to the middle portion of the drive shaft.

Abstract: According to one embodiment of the invention, a system for power generation inside a steering tool includes a drive system having a drive shaft disposed within a wall of the steering tool, a rotating shaft rotatably coupled to a non-rotating sleeve of the steering tool, and a spline coupled to the rotating shaft. The spline is operable to indirectly drive the drive shaft by directly coupling to an idler gear of the drive system.

Abstract: According to one embodiment of the invention, a rotary steerable tool includes a drive shaft configured to be coupled to a drill string at an upper end thereof and configured to be coupled to a drilling tool at a lower end thereof. A middle portion of the drive shaft is disposed axially between the upper and lower ends and has a smaller diameter than each of the upper and lower ends. The drive shaft further includes a housing rotatably coupled externally to the drive shaft and at least one housing module coupled to a respective opening in the housing at an axial location corresponding to the middle portion of the drive shaft.

Abstract: According to one embodiment of the invention, a rotary steerable tool includes a drive shaft having an upper portion configured to be coupled to a drill string and a lower portion configured to be coupled to a drilling tool. The drive shaft has a middle portion disposed between the upper and lower portions, the middle portion having a smaller diameter than each of the upper and lower portions. The tool further includes a housing rotatably coupled externally to the drive shaft at an axial location corresponding to the middle portion of the drive shaft, the housing formed from at least two housing segments configured to be coupled to each other substantially parallel to a longitudinal axis of the housing.