Equilibrium inclinations of straight boreholes

This paper describes a directional drilling model for calculating the equilibrium inclination of straight boreholes, considering a bottomhole assembly (BHA) with a "push-the-bit" rotary steerable system (RSS). The model yields closed-form expressions for the magnitude and orientation of the RSS pad force, which is required to maintain the inclination of the borehole. The explicit dependence of the RSS force on the positions of the stabilizers and the RSS, on the mechanical properties of the BHA, on the characteristics of the bit, and on the weight on bit enables the identification of particular cases of practical significance.