Drilling a borehole with a steering system using a modular cam arrangement

A rotary steerable system (“RSS”) for use with a drilling fluid, comprising:

• a steering head;
• a cam system comprising:
• a housing comprising a housing central axis;
• a cam positioned at least partially within the housing;
• and
• a solid cam shaft engaged with the cam and positioned at a fixed offset at least partially within the housing such that the solid cam shaft is rotatable about a cam shaft central axis,
• wherein the cam is rotatable to adjust or maintain an azimuthal orientation of the solid cam shaft;
• and
• wherein the drilling fluid is flowable in an area between the solid cam shaft and the housing;
• a hollow constant velocity (“CV”) shaft comprising a CV central axis;
• a shaft cap coupled to the solid cam shaft at an end opposite of the cam and also coupled to the CV shaft, wherein:
• the shaft cap comprises a bore and a channel to allow the drilling fluid to flow from an area outside the shaft cap between the solid cam shaft and the housing into the bore of the shaft cap;
• and
• the shaft cap is pivotable to pivot rotation of the solid cam shaft at the azimuthal orientation to rotation about the CV central axis;
• and
• a drill bit engaged with the CV shaft.

A method for drilling a wellbore into a formation comprising:

• deploying a drill string comprising a rotary steerable system into the wellbore;
• rotating a drill bit by rotating the rotary steerable system (“RSS”) to rotate a hollow constant velocity (“CV”) shaft to which the drill bit is coupled, which also rotates a solid cam shaft of the RSS positioned at a fixed offset;
• adjusting an angular direction of the drill bit by rotating a cam of the RSS to rotate the solid cam shaft and adjust an azimuthal orientation of the solid cam shaft, which adjusts an azimuthal orientation of the hollow CV shaft and the drill bit;
• pivoting rotation of the solid cam shaft to rotation of the CV shaft using a shaft cap coupling the solid cam shaft to the CV shaft;
• flowing drilling fluid through the RSS in an area outside the solid cam shaft, through a channel of the shaft cap and into a bore of the shaft cap, through the hollow CV shaft, and to the drill bit;
• rotating the cam to maintain the azimuthal orientation of the solid cam shaft and thus the drill bit;
• and
• drilling the borehole with the drill bit in the azimuthal orientation.