Dynamic Characteristics and Experimental Research of Dual-Piston Axial Oscillation Drag Reduction Tool

Aiming at the problem of low drilling efficiency of oil and gas wells due to the high friction during the drilling, a dual-piston axial oscillation drag reduction tool (DAOT) is proposed to reduce friction for long drill string in this paper. Using the proportional experiment methods based on the ground experiment conditions, pressure drop, axial displacement, and acceleration of DAOT were tested with different input parameters. The pressure drop calculation model was established by fluid mechanisms applied, and the axial excitation displacement model to the damped elastic rod subjected to axial external excitation was deduced. Furthermore, combining with the same parameters as the experiment and field application, the dynamic characteristics are studied by numerical calculation methods to identify proposed models. The results show that the correctness of the models is verified, the working pressure drop, axial displacement, working frequency, and axial oscillating force are all dependent on the input flow, the working frequency is positively correlated with the input flow, and the more the input flowrate, the great is its influence on the oscillating force. The application of DAOT can reduce extremely the friction force of drill string and improve availably the drilling efficiency. These conclusions can be of benefit for optimizing multi-piston axial oscillating tool and DAOT field applications.