Experimental study of feasibility of carbon dioxide storage in unmineable coal seam

The carbon dioxide usually performs as a kind of supercritical fluid when it is being injected into unmineable coal seam. The injecting process will cause a series of mechanical structure changes such as the cubical expansion, the shrink, the change of pore structures and so on, which will cause the permeability change of coal seam. It will also affect the process of adsorption, desorption and diffusion of methane. In order to find out the law of permeability change of coal seam and the displacement of methane during the carbon dioxide injecting process, some laboratory experiments had been done. The experiments contain the single-phase adsorption and the competitive adsorption of carbon dioxide and methane in coal sample, the displacement experiment of methane and the permeability tests of coal sample. The results show that under the same situation, carbon dioxide is easier to be adsorbed by coal sample than methane. During the process of injecting carbon dioxide into coal containing gas, methane will be displaced with high efficiency. The permeability of coal sample changed a lot before and after the injecting process which is helpful to improve the efficiency of methane drainage. The paper provided a reliable basis to store carbon dioxide effectively and safely in unmineable coal seam.