The theoretical bottomhole analysis of drillstring assemblies and the prediction of wellbore trajectories play an important role for directional drilling. Time constraints, cost efficiency and accuracy require computer aided planning of the drilling process. As such a program should be user friendly and, at the same time, accurate, a program was developed for personal computers, combining simplicity even for less experienced users with complexity as regards the sophisticated computation of the directional drilling behaviour of a variety of bottomhole assemblies.

The program is based on a newly developed three dimensional static drillstring analysis model for arbitrarily shaped boreholes. For any string assembly the wall contact problem is solved using a non-linear wall potential equation. The program allows sophisticated wellbore prediction calculations using an improved version of Ho's formula.

The numerical results could be verified by field data; even the walk tendency is well predicted.

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