Abstract:

To advance the development of near-bit measurement while drilling technology for underground coal mines, the feasibility of Bluetooth, electromagnetic wave and acoustic signal transmission was compared based on an analysis of the unique underground coal mine application scenarios. Bluetooth was selected as the preferred method for near-bit data transmission, and a wireless communication technical scheme across screw drilling tools was proposed. The transmission characteristics of Bluetooth wireless signals in water were investigated, and a wireless communication simulation model was established to determine the effects of transmission power, transmission medium, and transmission distance on Bluetooth signal strength. On the basis of overall scheme design and simulation analysis and optimization, the structure, circuitry and programs were developed, and an across screw tool wireless communication device was fabricated. Laboratory water circulation tests were conducted, and the functions of power supply, data acquisition and transmission were executed normally. The theoretical analysis, simulation results and laboratory test results were in good agreement, confirming the rationality and feasibility of the signal transmission characteristic analysis. A surface drilling test was carried out at a test base, with a footage of 249 m. The device provided a wireless channel for near-bit parameters, including gamma, torque and vibration, to be transmitted across the PDM drill, enabling two-way interactive communication. This work provides key technical support for the development of near-bit MWD technology for underground coal mines.