The Mechanism Of Burning Coal On Enhancing Coalbed Methane Recovery

The coal reservoir in our country has the characteristics of high degree of metamorphism,high fixed carbon content,development of the nanoscale pore,strong adsorption ability and high air content,but the coal reservoir contains fewer large pore and micro cracks.macro porosity,permeability,diffusion rate and production are very low.What's more,the low gas production wells occupied large proportion of Coal-bed Methane?CBM?wells.The above comprehensive factors are seriously affect the overall development and benefit of CBM.there is an urgent need to explore and develop the new technology and method to improve CBM well production and recovery according to the characteristics of China's coal reservoir.This paper proposed the concept of burning coal,which is a new technology on enhancing CBM recovery,based on the research of development status and output mechanism of CBM in our country.By injecting the air to gas injector wells,then use artificial ignition system to ignite coal seam,result in partial combustion of coal seam,and use the temperature and pressure sensors in down-hole for real-time monitoring,finally achieve the goal of enhanced CBM recovery.According to the related experiment and theory,analyzed the mechanism,key technology and the feasibility of burning coal.This paper established the single layer cylindrical wall heat conduction model of steady temperature and the CO₂ flooding gas theory model which is based on the principle of IAS multicomponent adsorption,and made a simulation and prediction about the effect in further.Through studying the mechanism of temperature and CO₂ on enhancing CBM recovery,it found that the adsorption capacity decreased with the increase of temperature,The desorption rate of coal reservoir increased with the increase of temperature.The diffusion coefficient of coal increased linearly with the increase of temperature,The mechanism of CO₂ on enhancing CBM recovery by competitive adsorption,filter replacement,increasing permeability,and promoting desorption etc.Take Hancheng mining area as an example,this paper made a simulation research on gas displacement effect based on the factors of temperature and CO₂ respectively by themethod of control variable.The study found that the recovery rate increase amplitude increased significantly with the rise of temperature.The recovery rate increase amplitude increased with the increase of heating radius.The recovery efficiency increased with the increase of CO₂ displacement radius.The recovery rate increase amplitude increased with the increase of CO₂ concentration,but it is not always on the increase,when CO₂ concentration reaches a certain value,recovery efficiency increase amplitude decrease with the increase of CO₂ concentration.