MODEL AND METHOD FOR A TIME-EFFICIENT ANALYSIS OF LATERAL DRILLSTRING DYNAMICS

摘要

The lumped parameter model and numerical method proposed in this paper aim at gaining a better understanding of the mechanisms leading to harmful lateral drillstring vibrations in inclined boreholes. The shooting method is applied to the equations of motion in order to skip transients and to arrive quickly at a steady state solution. In combination with a sequential continuation technique, parameter maps are generated that show regions where harmful vibrations can be avoided. Comparisons to a finite element model show that the steady state is predicted accurately, while consuming only a fraction of the computational time. The proposed model is experimentally validated on a test rig. Special emphasis is put upon the evaluation of contact forces and the frequency content of the signals. The presented investigations create the basis for real-time analysis of drillstring dynamics and can be used to give recommendations to adjust operational parameters.