Dynamic state-feedback control of nonlinear three-dimensional directional drilling systems

Directional drilling systems generate complex curved boreholes in the earth's crust for the exploration and harvesting of oil, gas and geothermal energy. In practice, boreholes drilled with such systems often show instability-induced borehole spiraling, which negatively affects the borehole quality and increases drag losses while drilling. This paper presents a dynamic state-feedback controller design approach for the stable generation of complex, three-dimensional borehole geometries, while avoiding undesired borehole spiraling. The design is based on a model for three-dimensional borehole propagation in terms of nonlinear delay differential equations. After casting the problem of borehole propagation into a tracking problem, it is shown that complex, three-dimensional borehole geometries can be asymptotically stabilized with the proposed controller. The effectiveness of the proposed approach is evidenced in an illustrative benchmark study.