Experimental study on gas diffusion law of drill cuttings during the whole desorption process

摘要

Gas diffusion law of drill cuttings can be used for forecasting coal and gas outburst risk and de termining gas content in coal seam. According to spherical shell losing stability mechanism, outburst and field measurement of gas content in coal seam have close relation to initial gas flow after coal is broke up by crustal stress. Whereas, many researchers only investigated gas diffusion law of drill cuttings which ap peared after 10 s due to the restriction of test methods and cognition. Measuring device of gas flow from drill cuttings was devised according to one-dimensional gas dynamics principle, gas diffusion law during the whole desorption process was measured by using sensor and computer data acquisition technology; then test data was analyzed by using curve fitting toolbox of MATLAB, curves of gas diffusion law were ac quired. Research results show that gas flow from drill cuttings achieves maximum value as soon as diffusion process begins, flow crest appears at the same time, and then attenuates to zero gradually. Dead space re sults in the appearance of flow crest, whose appearance time has relation to spout area of coal sample con tainer. At interval between zero to t, curves of gas diffusion law occur a horizontal asymptote ( viz. Qp = 0) , but the vertical asymptote (viz. Qv = Qvoo ) which proved by few researchers doesn' t occur.