Mechanism analysis of friction reduction in coiled tubing drilling with axial vibratory tool

Abstract

Abstract In order to investigate the friction reduction mechanism of the hydraulic axial vibratory tool in coiled tubing drilling (CTD), a dynamic model is proposed by introducing the Coulomb friction term to the wave equations in this paper. Then a retrogressed case is selected to validate the model and both the results of two models display an excellent consistency. Finally, the effect of tool parameters (frequency, average drag force, installation position), CT parameters (size, rate of penetration) and wellbore parameters (coefficient of friction, wellbore curvature) on the tool performance are analyzed with the proposed model. The results indicate that the axial force reduction at the vertical end is mainly affected by the frequency, amplitude, installation position and coefficient of friction (CoF), whereas the CT size, rate of penetration (ROP) and wellbore curvature affect the tool performance slightly. Based on the study, it reveals the action mechanism of the tool in CTD that the force reduction mainly caused by the direct traction of the tool and the corresponding friction reduction at the curved and buckling section.