An experimental study of the effect of hydraulic vibrations on initiation of buckling and axial force transfer for helically buckled pipes at simulated horizontal wellbore conditions has been conducted. Hydraulic vibrations have been induced inside the drillpipe by interrupting the fluid flow at controllable frequencies. The results show that the hydraulic vibrations induced inside the drillpipe can reduce the buckling force by 11% to 45%. These results were collected by buckling the pipe with and without vibrations and comparing the loads at which buckling is initiated. It is also noticed that the friction force between the pipe and the wellbore and the stick-slip motion are reduced when compressing the pipe while inducing the vibrations. Regarding the effect of hydraulic vibrations on the axial force transfer, an increase in the axial force transmitted from the top end of the facility to the bottom end of the facility by 30% to 100% was found. This increase depends on the fluid flow rate, frequency of the vibrations, fluid type (i.e. viscosity) and magnitude of the applied top load. It was found that this technique highly depends on the viscosity of the drilling fluid used. Polymers showed a different behavior compared to water. They were found to have a damping effect on the pressure pulses, therefore are less efficient compared to water. The results of this study are important for extended reach drilling; i.e., reducing the friction due to buckling of coiled tubing and reducing torque and drag in the case of drillpipes and casing in horizontal wellbores.
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Barakat et al. (2007) studied this question.