Dynamic Research and Experimental Analysis of a New Downhole Drilling Tool

Abstract

With the increasing of drilling depth, the working conditions of the drilling engineering are becoming more complicated. When drilling in the complex well structure, there are many new problems or challenges such as low rate of penetration (ROP), serious stick–slip phenomenon, or high risk of downhole tools failure. The most critical factor in solving these new challenges is improving rock breaking efficiency. Considering this, this paper proposed a new oscillator based on the positive displacement motor. Combining with new complex drilling conditions, the new structure was designed. The mathematical models were presented, including the working mechanism of the new design with its structure parameters. Furthermore, the theoretical models of dynamics under new conditions were analyzed, including the new bottom hole assembly. Based on this, we can get the vibration displacement, velocity, and the system vibration spectrum at different drill string positions. Compared with the results of a numerical example, the lab test was carried out. The two important parameters of vibration frequency and impact forces were compared with the theoretical results, which verified the correctness of the theoretical model and the accuracy of the solution method. Moreover, field experiments were also tested to verify the results, and the field experimental data showed that the new design could increase ROP obviously. The method and conclusions of the research can provide a new reference for the new downhole technology of enhancing the ROP or improving the rock breaking efficiency in complex well structure.