Experimental study of aerospace solid propellant fracturing in simulated coal sample

Coal reservoirs with high gas content and low permeability seriously restrict the efficient production of coal and coalbed methane. It is necessary to fracture and enhance the permeability of coal reservoirs. Aerospace solid propellant deflagration can generate a large amount of high-energy gas to impact coal reservoirs, which can achieve the purpose of fracturing and enhancing permeability of coal reservoirs. To study the characteristics of aerospace solid propellant for fracturing coal, a solid propellant for fracturing and permeability enhancement of coal reservoir was firstly researched and developed based on the formula of civil aerospace solid propellant, was, and its performance, sensitivity, pressure and temperature resistance were tested. The aerospace solid propellant fracturing test was then carried out using simulated coal samples, and the borehole wall pressure and strain within the simulated coal samples were monitored during the test. Finally, the destruction characteristics of simulated coal samples were analyzed according to the test results. The results shown that the aerospace solid propellant had good performance, with the advantages of waterproof, pressure resistant, and no CO generation, which could be adapted to the underground environment of coal mine. During the test, the time curve of the borehole wall pressure shown the stages of rapid pressure rise, slow pressure rise, and nonlinear pressure drop, in which the rise time of the borehole wall pressure was about 18 ms. The peak pressure in the borehole was low and unevenly distributed. The peak pressure in the middle of the borehole was 118.1 MPa, and the peak pressure at the bottom of the borehole was 85.3 MPa. Stress wave generated in simulated coal sample during aerospace solid propellant fracturing was composed of compressive and tensile phases with low intensity, long duration and slow decay with distance. The aerospace solid propellant fracturing technology was dominated by the quasi-static action of high-energy gas, with high utilization of stress wave energy. The research results provide a reference for the application of aerospace solid propellant in the field of coalbed methane mining.