Experimental Study of Hydraulic Cavitation Tool for CBM Production Enhancement

To address the problem of high adsorption of coalbed methane (CBM), a hydraulic cavitation tool for CBM production enhancement was designed based on the mechanism of cavitation wave promoting CBM production enhancement. To achieve the best cavitation performance and generate high-intensity cavitation waves to promote CBM desorption, the influence of inlet flow rate and upper and lower nozzle diameter ratio on cavitation performance was investigated by CFD technique and cavitation jet experiment. The simulation and experimental results show that as the inlet flow rate increases, the cavitation effect in the oscillation chamber increases, and the throttling pressure difference increases, so the throttling pressure difference is used to characterize the cavitation performance of the cavitation tool. The cavitation performance of the cavitation tool is analyzed when the upper and lower nozzle diameter ratio is from 1.5 to 3 and the inlet flow rate is from 2  to 10 m³/h. When the upper and lower nozzle diameter ratio is 2, the inlet flow rate is 6 m³/h, the throttling pressure difference increases by 73.2%, the value of vapor volume fraction increases by 77.7%, the cavitation effect no longer increases, achieving optimal cavitation performance. As a result, the high-intensity cavitation waves generated by the cavitation tool can continuously propagate in the formation, play a continuous oscillating effect on the coal seam, and can significantly increase the gas production of coalbed methane. The research results can provide new ideas for the development of CBM production enhancement tools.