Experimental Research On Influencing Factors Of The Gas Content In The Coal Bed With The Method Of Drilling Desorption

Coal seam primitive gas content gas emission volume forecast an important basis for the parameter, which determines the important work of the mine gas level, the mine ventilation design, gas drainage, outburst and gas management.This paper will focusing on the factor of gas content measurement in laboratory platform like exposure time, sampling method,sample weight and size,and loss gas content calculation.In the laboratory simulation test we have get some conclusions. The relative error of gas content by drilling desorption method is increased with the exposure time; The core method of gas content results more accurate than the cuttings method; In exposure time within 15 min, the results of gas content by drilling method and coring method are similar, but with the increase of exposure time, the error increases. The desorption gas content, residual gas content and loss gas content by drilling method are increasing with the sampling weight of 180 g,it remains consatnt when sampling weight reaches 240 g. The smaller the particle size of coal samples is, the greater it will result in desorption rate and loss gas content, meanwhile, the smaller amount of residual gas is and the result error is greater; the result of gas content by drilling desorption method increases with the sample particle size. As for the option of coal samples, we screened out those whose diameter is more than 1mm when using drilling desorption, while those with diameter ranging from 5 to 10 mm were prepared when adopting coring method. The negative exponential method calculates know that,on a scale of 0~12 minutes the result of barrell model calculation is best in accuracy, after 12 min, the result of power function prediction is most accurate; a modified formula according to different calculation model for predicting gas loss content with different exposure time is developed.Finally, the results of this paper is applied to laboratory determination of gas content for anthracite coal, gas coal, lean coal and bituminous coal. Results show that gas content determination error is singnificantly reduced, which is lower than 10%, and achieves the accuracy of field engineering.