Experiment And Principle Of Improving Coalbed Methane Recovery By Vibration Wave And Artificial Electric Field

The migration of coalbed methane needs to go through three complex physical and chemical processes: desorption,diffusion and percolation,and each stage affects the output.therefore,in order to increase the output,it is necessary to improve the desorption rate,diffusion rate and permeability of coalbed methane through relevant technologies and measures.It is considered that vibration wave and artificial electric field can play a role in coalbed methane development as physical incentive technology to improve coalbed methane recovery.therefore,the physical simulation experiments of diffusion,percolation and gas recovery under the action of vibration wave and artificial electric field are carried out respectively.Through the optimization and transformation of the seepage experimental instrument,the permeability of coal under the action of vibration wave is tested.The results show that the vibration wave can increase the permeability by 16.6%.The artificial electric field has little effect on the permeability,and it is considered that the strength of the electric field used in the experiment is low,which can not affect the percolation state of gas molecules in coal micropores.According to the diffusion experiment,when the vibration wave is loaded,the diffusion coefficient increases by 41%.Through the research and development of experimental instruments,the physical simulation experiment of drainage and mining was carried out.For the sake of safety,the experiment of using nitrogen instead of methane was carried out.In the state of natural gas production,the production decreases rapidly,and the decline rate is suppressed after loading the vibration wave,and the gas production becomes stable,but in the second cycle after loading,the output decreases rapidly;on this basis,the vibration is stopped and the output picks up after loading the artificial electric field.the same phenomenon is that the output decreases rapidly again after the third round after loading the electric field.Thus it can be seen that the gas recovery by loading vibration wave and artificial electric field is effective,but the general effective cycle is 2-3 cycles.According to the theories of molecular dynamics,electrochemistry,mechanicalvibration and conservation of momentum,the mechanism of improving coalbed methane production and recovery by vibration wave and artificial electric field is analyzed.It is considered that the mechanical vibration action of vibration wave will cause tension,compression and shear of coal medium,make the skeleton of coal matrix elastic deformation,produce more micro-cracks and micro-pores,and expand the diffusion and seepage channels.the diffusion rate and permeability are increased.The Joule heat effect of the vibration wave transfers the energy to the coal-methane system,the energy in the system increases,the irregular movement of molecules intensifies,the surface adsorption sites of the coal matrix decrease,and the adsorption capacity weakens,which is more conducive to the desorption of the gas;at the same time,the desorption rate and diffusion rate of the gas are increased with the increase of the temperature of the system.Under the action of electric field,the macromolecular structure of coal is polarized,resulting in a directional shift,which increases the adsorption potential of coal to gas,and strengthens the adsorption capacity of gas;at the same time,the thermal effect of electric field increases the internal energy of coal-methane system,and the irregular thermal motion of the two molecules increases,which increases the desorption rate and diffusion rate,and weakens the adsorption capacity of gas.There is a certain competition between the two thing.With the prolongation of the electric field action time,the thermal effect plays a more important role in the desorption and diffusion of the dominant gas.