Experimental Study on Fluid Transport Processes in the Cleat and Matrix Systems of Coal

The fluid transport phenomena were studied on a cleat-plug (with cleats) and a matrix-plug (cleat-free) of a Chinese coal under controlled confining stresses (10−40 MPa). The single-phase fluid flow tests with argon (Ar) and water were performed under the steady-state. The gas breakthrough tests (two-phase fluid flow tests) with helium (He), argon (Ar), methane (CH4), and carbon dioxide (CO2) were conducted on the water-wetted plugs under the nonsteady state by monitoring the gas pressure changes with time in two closed compartments separated by the plug. It was found that the permeability of both the matrix- and cleat-plugs for Ar and water are measurable under the test confining stresses and the steady-state. The cleats in the cleat-plug are not easily closed by the high confining stress, evidenced by the fact that the permeability of the cleat-plug under the 40 MPa confining stress is still higher than that of the matrix-plug under the 20 MPa confining stress. The permeability coefficient of a confined...