Page 47 - CBT 2018
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Directional drilling
Directional drilling has made it possible to drill deep boreholes that weave complex trajectories in the subsurface. A key factor in this ability to complete complex wells has been the emergence of rotary steerable systems (RSS). These servo-controlled downhole robots steer the drill bit by either applying a force
on the borehole wall or by tilting the bit. The directional propagation of the borehole depends on the force and moment at the bit; they are affected not only by the action of the RSS but also by the deformed configuration
of the bottom hole assembly, which is constrained by the stabilizers to espouse the existing borehole. The propagation of the borehole is thus governed by the interaction between the wellbore and the drilling structure. Study of this dynamical system is motivated by engineering issues, which include preventing borehole spiraling. [84–89]
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