Experimental measurement method of matrix and fracture permeability of coal and rock mass

WEI Mingyao; HUANGFU Haoqi; LU Chunqin; GAO Kang; YU Liyuan; GUO Fengxian

doi:10.13247/j.cnki.jcumt.20240458

Abstract：Coal body has a complex pore-fracture structure and can be regarded as a dual pore medium composed of matrix and fracture system.The flow behaviors such as fluid migration,gas adsorption/desorption,gas slip and diffusion in the matrix pores have important impacts on the overall fluid migration.Due to the inability to measure the matrix permeability independently,the single fracture permeability of the coal body is assumed to be the overall permeability in many studies.The controlling role of the matrix permeability in the overall flow process is ignored usually.Based on the permeability deviation characteristics caused by the gas slippage effect in the matrix,this paper presents a measurement method of the coal matrix and fracture permeability.By calculating and processing the overall permeability data of different coal samples,the evolution laws of the matrix and fracture permeability of the tested coal sample under different effective stresses are obtained.Meanwhile,the fracture permeability value of the coal body under no load is obtained by high-precision CT scanning of the coal samples,and the accuracy of this measurement method is verified by comparison.The results show that for the same coal sample,under the same effective stress,the matrix permeability is 2 to 3 orders of magnitude smaller than the fracture permeability;for the four different sets of tested coal samples,both the matrix and fracture permeability gradually decrease with the increase of effective stress.But due to the different metamorphic degrees of the coal samples,the reduction amplitudes are also different,with anthracite having the most obvious decrease,followed by lignite,and bituminous coal having the smallest.