Forecasting Of Coal And Gas Outburst Using Desorption Indexes Of Drilling Cuttings

Coal and gas outbursts are dynamic disasters,which not only affects coal production but also threatens the lives of coal mine workers.Pingdingshan No.6 coal mine situated in Henan Province,China is an outburst prone coal mine with high frequency.The main coal seams of coal mine contain high gas pressure and gas content.In order to study the influence of gas on outburst risk of coal seam in No.6 mine of Pingdingshan Coal Group,four coal samples were collected from two coal seams（Ding5-6 and Wu 9-10）.The samples were crushed and sieved into three kinds of particle sizes to conduct experiments of proximate analysis,firmness coefficient,and adsorption/desorption test,and desorption indexes of drilling cuttings（K₁ and?h₂）.The pore structure of coal was determined and analyzed by low-pressure N₂（77K）/CO₂（273K）adsorption method.The results of proximate analysis show that the M_ad content,A_d content and V_daf content of coal are ranging from 1.39-1.53%,17.85-29.69.8%and33.8%-34.8%.The coefficient of coal firmness is 0.10-0.71.The range of adsorption capacity（V_L）of coal is 24.11-28.8 m³/t while adsorption constant b is 0.54-0.77.The analysis results of coal pore structure show that the pore volume and specific surface area obtained by DFT Model are 0.033-0.039 cm³/g and 101.18-111.87 m²/g respectively,which constitute the main adsorption space of methane.The BJH pore volume and BET specific surface area of coal is ranges from 0.014-0.032 cm³/g and2.81-4.78 m²/g,The BJH pore volume and BET specific surface area of coal is ranging0.014-0.032 cm³/g and 2.81-4.78 m²/g,which provided the main diffusion space for methane.The results of gas desorption experiment in 120min revealed that gas desorption capacity of coal sample is positively correlated with the gas pressure,and desorption capacity of gas increases with the increase of the equilibrium pressure.The experimental analysis of 120min desorption under different pressures shows that the initial desorption rate of gas from coal sample is fast,and gas desorption rate of gradually slows down with rise of desorption time.The experimental results of desorption indexes of drilling cuttings indicated that gas pressure is related by a power function to K₁ and?h₂.Additionally,a linear function relationship between gas desorption indexes of drilling cuttings was verified by experimental and theoretical analysis.The reliability tests of among measured and calculated values of desorption indexes of drilling cuttings K₁ and?h₂ was carried out,and it is evident from results that?h₂ is more reliable for outburst prediction.Based on the sensitivity measures of coal and gas outburst of No.6 mine of Pingdingshan Coal Group,the critical value of coal and gas outburst was obtained.The relationship between the gas pressure and gas content of coal seam Ding 5-6 and Wu 9-10 was analyzed by using the classic W-P model.