1. Field of Invention
The present disclosure relates to a system for controlling a path of a drill bit in a subterranean formation. More specifically, the present disclosure relates to a steerable drilling assembly having a collar with an axial bore formed oblique to an axis of the collar.
2. Description of Prior Art
Earth boring drilling systems are typically used to form wellbores that intersect subterranean formations having hydrocarbons so that the hydrocarbons can be extracted from the formations. The drilling systems usually include a rotatable drill string having a drill bit on its lower end for excavating through the formation. The drill string and drill bit are typically rotated by either a lop drive or rotary table provided on surface. The types of drill bits are usually either roller cone bits or drag bits; and where cutting elements are generally formed on the bits. The combination of axial pressure on the drill string, combined with drill string rotation, causes the cutting elements to excavate through the formation and form cuttings that are circulated back uphole with drilling fluid.
Non-vertical or deviated wellbores are sometimes formed by whipstocks that are disposed in the wellbore and deflect the bit and drill string along a designated path in the formation. Deviated wellbores are often formed using mud motors mounted onto the drill string, which have fixed or adjustable angle bent sub housings and, when used in a sliding only mode are selectively oriented to direct the bit along a chosen direction. Deviated wellbores are otherwise formed using rotary steerable systems, which provide a means of steerable drilling while also permitting most or all of the drill string to rotate during steering operations.