Optimization of borehole spacing of gas extraction based on the method of structure curvature

Reasonable borehole spacing is one of important measures to reduce gas content of coal seam and number of drilling holes. Based on the gas geological data in Sihe mine, combined with the method of structure curvature, of distinguishing coal body structure by well logging and of testing stress-strain-permeability in experiment and so on, the corresponding relationships among the permeability of the coal seam, coal body structure and the structure curvature were gained. Based on these studies, according to the motherboard contour line in 3304 working face, the permeability distribution law in working face was predicted. Based on the law of conservation of energy and Darcy's law, the mathematical model of influent radius under different extraction pressure, extraction time, permeability, gas pressure and aperture was established. According to the results of permeability prediction and the mathematical model of influent radius, the reasonable borehole spacing in different areas of the working face was determined. Field practice showed that this method determined the drilling holes spacing by size of the osmotic coefficient can reduce the amplitude of variation of the gas emission and reduce the number of drilling hole. It can be used as a theoretical guidance to determine borehole spacing in others similar geology tectonic regions.