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In order to solve many problems occurred in the initial development period of the new coal reservoir fracturing and permeability improvement technology with high accumulated energy electric impulse stress wave, the electric impulse stress wave loading experiment and micro-location observation means were applied to the study 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 impulse 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 would 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 crack 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 structural 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 reservoir permeability improvement and reconstruction measures. [ABSTRACT FROM AUTHOR]

A coal reservoir excitation by the repeated strong pulse waves of high energy accumulation was an originality new technology developed by Chinese scientists based on the principle of the nuclear explosion shock wave. The discovery of the preliminary work showed the permeability improved feasibility and availability of the coal reservoir. But the basis study lagged behind the engineering discovery and the further research and development and the promoted application of the technology were urgently needed to make a breakthrough at the bottleneck of the basis study. Faced to the major technical requirement of the high efficient economic development of the coalbed methane in China, the paper analyzed the study status on the shock wave fracturing and permeability improved field of the coal reservoir, stated the basic principle of the coal reservoir fracturing and permeability improved with the repeated strong pulse wave of the high energy accumulation, summarized the preliminary site experiment of the technology and the engineering discovery effect, and refined the scientific problems to be solved along the direction. The paper discussed the breaking dynamics features of the coal reservoir and the coupling role mechanism of the geological and engineering factors under the guidance of the repeated strong pulse waves of the high energy accumulation, in detail explained the key scientific problem of the wave-flow-coal interreaction under the guidance of the repeated pulse waves, which would be the most important basis to further research and development and to improve and apply the permeability improved technology of the coal reservoir. [ABSTRACT FROM AUTHOR]