Numerical simulation and experimental study on improving gas drainage by hydraulic fracturing

Abstract

ABSTRACT To address the difficult problem of coal seam gas control that has arisen as a result of the recent development of deep coal mining, hydraulic fracturing technology is applied to the coal seam, the dual porous medium theory is used, and a multi-scale flow model of coal gas is constructed under certain assumptions. The dynamic evolution law of coal porosity and permeability is studied according to the gas multi-scale diffusion equation, gas-bearing coal seepage equation, and other theories. To study the variation law of important parameters such as coal seam pressure and drainage influence range in the process of coal and gas drainage, numerical simulation software is used, and industrial tests are supplemented to verify energy efficiency. The study found that using hydraulic fracturing technology to enhance the permeability of coal seams can significantly improve the average gas extraction concentration, and the maximum increase in the extraction net flow after fracturing is about 60% compared with that no fracturing, and can effectively suppress the attenuation of the extraction flow due to the extension of the extraction time, effectively improving the gas extraction effect of the test borehole. Simultaneously, if other auxiliary measures are implemented, the permeability enhancement effect may be more stable.