Static and Dynamic Three-Dimensional Bottomhole Assembly Computer Models

Abstract

Summary This paper presents two three-dimensional (3D) mathematical models to predict the directional behavior of bottomhole assemblies (BHA's). The first model describes BHA dynamic, stepwise, transient behavior. Displacements and lateral forces, computed for each step, account for friction against the borehole wall. The second model computes a static BHA equilibrium whereby simplified friction forces are assumed. The static lateral forces are found to be an average of the highly varying ones computed by the dynamic model, but the static computer run is much faster. The static model is therefore used iteratively to compute an oriented dogleg severity that balances lateral forces. This is used to derive the directional behavior of the BHA. Comparison and calibration against real field cases are performed.