Petrology Analysis Effect For Enhancing Coa Permeability With Repetitive Electric Pulses Wave

Based on the simulation experiment of different rank coal samples with electric pulse wave(EPW) and mainly using the method of coal petrology, the expansion characteristics of the pore and fracture of coal samples was investigated, the responses of coal petrology factors to the EPW loading were discussed, and the matching of the coal properties to the loading conditions was analyzed. Results show that the pore development is a process expanding from small to medium and large pores and, then, large and medium pores continue to expand up to connect fractures. With increasing the EPW impact times, the pore volume trends to the fluctuant enlargemen, which reflects the degree of the pore structure adjustment. Expansion of the micro-fissures in fat coal are initiated mainly from telocollinite and those in anthracite are mainly embodied as the widening of previous fissures. Microhardness of the fat and lean coals is lower but that of the anthracite is very high. Micro- brittleness in the lean coal is highest and the microfissure develops best. Expansion effect of the micro-fissures in the fat coal is most strong, which results in the specific coal rank. Development of the micro-fissures in coal has the maceral selectivity. It was found that the density of the micro-fissures in vitrinite group is highest while the width of those is relatively larger. Weak mechanical properties zones in the fat coal occur in telocollinite or vitrain bandes, leading to the premature rupture of the bandes and uncompleted developmen of the micro-fissures under the energetic bomb action. It is also found that the coal can be destroyed by the lower EPW stress, which crucially initiates the structural defects in coals. The stress is fouced around the defects, leading to the fissure initiation, propagation and instability of coal body due to the fatigue fracture. As far as the fracturing efficiency is concerned, the metal discharge wire is more suitable for fracturing the pores in coal while the containing-energy bomb is more suitable for reconstructing the fissure in coals. In other words, the low-power and repeated EPW loading is more favorable to the expansion of the pores in coals, and the high-power EPW loading can induce preferentially the expasion of the fissures.