Development of fully coupled deviated well drill string dynamics simulation model for fatigue and vibration analysis.

Drilling is an expensive but necessary part of mining, geothermal and oil operations. The cost of drilling can be reduced using simulation models to optimize parameters and perform fatigue prognoses, expanding the useful life of downhole equipment. However, current state-of-the-art simulation models have limitations in modeling drill string dynamics in the build section and generating stress history for drilling and tripping operations. This paper presents a model with an efficient contact algorithm, reconfigurable stiction/friction submodels, accurate boundary conditions, expanding drill string length as the bit advances and readily available stress history for any component. The model predicts the onset and location of wellbore contact, as well as axial, lateral and torsional vibrations in any well section. Multiple well trajectory simulations are presented, showing responses such as whirling and snaking. Stress histories and predicted fatigue life of components are compared, showing how the model can be used for selecting the best well trajectory and drilling parameters during well planning. These case studies also show that dogleg severity and kick-off point of the deviated section influence the fatigue life of the downhole components.