Objective The balancing device for a fully hydraulic top drive drilling system (TDDS), an important part of a drilling rig capable of 10000-m-deep drilling, is designed to dynamically and accurately regulate the axial load in the screwing and unscrewing processes. This helps protect the threads of drill rod connectors from damage, thereby ensuring the stability and safety of drilling operations.
Methods This study designed a balancing device with a hydraulic circuit for the SP.TD-01A fully hydraulic TDDS, aiming to achieve the balancing and bouncing functions required during the application of the TDDS. First, this study determined the structure and principal operating parameters of the hydraulic circuit of the balancing device for the TDDS. Then, using the Matlab/Simulink/SimScape simulation platform, this study constructed dynamic simulation models for the hydraulic circuit and for the screwing and unscrewing mechanisms of the spindle and drill rod of the TDDS. Using these models, this study simulated and tested the axial load change and displacement characteristics of the spindle protection connectors of the TDDS in the screwing and unscrewing processes, as well as the flow and intensity of pressure characteristics and energy consumption indicators of the hydraulic circuit.
Results and Conclusions The results indicate that the balancing device designed for the TDDS demonstrates a reasonable functional structure and high dynamic regulation performance. At a spindle speed of 10 r/min, screwing and pretightening were completed within 24 s, and unscrewing and releasing consumed 26 s. During the screwing operation, the pressure on the threaded surface reached a maximum of 11.2 kN, stabilizing at around 550 N. During the unscrewing operation, the pressure on the threaded surface exhibited a maximum of 3.5 kN and an average of about 1.2 kN. After the unscrewing operation, the TDDS bounced off the drill string for a distance of 76.5 mm. The designed balancing device for the TDDS and its hydraulic circuit were applied to the SP.TD-01A fully hydraulic TDDS, yielding satisfactory application results and playing a vital role in protecting the threads of drill rod connectors. The spindle protection connectors of the TDDS were replaced only four times for safety reasons during the drilling of well SK-2. This study can serve as a guide for the further research and development of TDDSs.
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