In spite of research efforts to develop a numerical model for predicting wellbore trajectory, there isn’t an adequate model for simulating new hole creation and predicting wellbore curvature and build rates that accounts for bottomhole assembly (BHA) dynamics, geometric constraints, rock properties, and steering tool action.

This paper presents new, comprehensive 3D model of BHA dynamics for lateral and torsional modes of motion. This model includes the presence of stabilizers and sections with different geometric and mechanical properties along the BHA. It considers changes in trajectory due to action of bent subs or rotary steerable systems (RSS); allows for abrupt changes to friction factors during transitions from sliding to rolling motions in the wellbore; and accounts for the effects of the bit’s side-milling capacity and side load changes due to changes in the formation.

The DYNTUB software, an advanced simulation tool for predicting well trajectories while drilling, was developed based on this model. This paper presents a mathematical model for the BHA and the well trajectory, the numerical integration method, and the results calculated for various examples steering tools and formations.

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