Investigation of Pipe Rocking and Agitator Effectiveness on Friction Reduction during Slide Drilling

Abstract In this paper, we present a comprehensive friction reduction model to investigate the combined effects of pipe rocking and drilling agitator tools (DAT) on friction reduction during slide drilling. The drillstring torsional oscillations resulting from pipe rocking and axial oscillations induced by the DAT are described in terms of the damped torsional and axial wave equations, respectively. Downhole damping effects mainly from the drillstring-wellbore contacts make the torsional and axial oscillations coupled with each other. Taking account of the differences in the nature of excitation and boundary conditions for torsional and axial oscillations, the finite difference method and augmented transfer matrix method are used for solving the torsional and axial dynamics, respectively. Parametric studies have been carried out to first analyze the separate influence of pipe rocking and the DAT operating parameters on the friction reduction. Simulation results show that optimum friction reduction is hard to achieve with either pipe rocking or the DAT alone due to the existence of a section of drillstring subject to static friction. We then simulate the combined effects of pipe rocking and the DAT techniques, which are capable to eliminate all the static friction along the whole drillstring via parameters optimization. The proposed model can be used as an advisory tool and is well suited for a real-time implementation due to its high computational efficiency.