Modeling and analysis of stick-slip vibration and bit bounce in drillstrings

Bit bounce and stick-slip vibration are detrimental to the service life of drillstring and down-hole equipment. A two degrees-of-freedom lumped parameters model is employed to account for bit-rock interaction and coupled vibration. Qualitative analysis to system parameters is performed through analyzing the influence of the angular speed of the rotary table and the length of drillstring on stick-slip vibration and bit bounce. After that, the suppression methods of stick-slip vibration and bit bounce are also given. The nonlinear motions predicted by the model are in agreement with the experimental observations. The study shows that increasing the weight-on-bit(WOB) and the angular speed of the rotary table effectively suppresses bit bounce and stick-slip vibration. What's more, the posterior models can suppress stick-slip vibration. At the same time, bit bounce can be reduced through applying the models in the middle. When the drillstring is in a higher-length, the stick-slip frequency is at a lower level. However, the intensity of bit bounce is extremely high.