Influence laws of modulated vibration on friction reduction in inclined-wells

Key words:  inclined-wells  drill string vibration  friction reduction by vibration  orthogonal experiment  parameters optimization

Abstract:

By coupling vibration of drill string and friction of borehole, a mathematic model was established according to the elastic rod theory to investigate the friction reduction caused by axial vibration of drill string during jarring in highly inclined-wells. This model was used to analyze the influences of the intensity of vibration force, vibration frequency, friction coefficient and the drilling fluid viscosity on the friction reduction effect. Orthogonal experiment was used to analyze the magnitude of the effects from those factors. The results show that improving the excitation intensity and frequency or reducing the friction coefficient and drilling fluid viscosity coefficient can effectively help friction reduction, and there is an optimum value for excitation frequency. Regarding to friction reduction effect magnitude, excitation intensity ranks the highest, and then come friction coefficient, excitation frequency and fluid viscosity coefficient.