Experimental study of displacing & replacing methane in low permeability coal seam by injecting liquid carbon dioxide
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Abstract:
This paper is to solve the gas drainage problem of low permeability coal seam. Based on the characteristics of liquid carbon dioxide with low temperature, viscosity, percolation resistance and phase change pressurization, the liquid carbon dioxide enhanced methane recovery technology was proposed to improve the gas drainage efficiency. Liquid carbon dioxide injection test was carried out at Sangshuping No.2 mine shaft,Hancheng mining area, and by which injection process was developed, the key parameters were determined and the methane extraction efficiency influenced by carbon dioxide was examined. The results show that the pressure of injecting is fluctuated. Initially, injecting pressure rises fast and then keeps stable when rising to 2.5 MPa.The flow rate of injection maintains from 0.6 m3/h to 1.4 m3/h and the total cumulant of liquid carbon dioxide is 6.0 m3. The concentration of carbon dioxide in the test borehole is taken as index, and it's found that the influence radius of the test is 18 m. The methane concentration and the purity in the test area are 2.5 and 3.5 times of those in the original data respectively, which proves the proposed technology enhances the gas extraction efficiency.
