Formation and development of coal micro-fractures under stress wave induced by electrical impulses

In order to solve many problems occurred in the initial development period of the new coal reservoir fracturing and permeability improvement technology wit h high accumulated energy electric impulse stress wave,the electric impulse stress wave loading experiment and micro-location observation means were applied to the stu dy on the micro crack occurred development process of the fat coal sample from Ordos Basin and the influence factors.The results showed that in the repeated electric imp ulse stress loading experiment,with the impact number increased,the micro crack line density would be increased and the formation of the new generated micro crack woul d come from the shearing stress occurred by the impact wave.The stress failure process of coal could be divided to three stages generally.The micro crack network of coal would be basically formed when the coal was impacted fourthly,there would be no coal cuttings occurred obviously,so impacted fourthly was the best condition.The micro cr ack network of coal would be mainly developed in the vitrinite band, new generated micro cracks would have a priority to start the expansion in the large size original struct ural defects. The electric impulse stress wave would have obvious fracturing and permeability effect of the coal and the original structural defects existed in the coal would be main part to have the coal micro cracks.The coal and rick bands type and other combined mode would be the important geological factor considered to set up the coal r eservoir permeability improvement and reconstruction measures.