Analysis Of Influence Factors On Gas Pressure Distribution Around Borehole

The permeability coefficient of coal seam is a symbol of the difficulty of gas flow in coal seam,and its size is one of the important factors that affect the law of coal seam gas flow.There are many measuring methods for permeability coefficient of coal seam,but there are some idealized assumptions in each method.In order to distinguish the advantages and disadvantages of each method,we need further research on the basic theory of gas flow law of coal seam.The coal seam permeability is closely related to the permeability coefficient,the size and occurrence state of stress,Klinkenberg effect,gas(gas desorption)is closely related to some scholars through experimental methods,and study the effect of each factor on the permeability of coal seam,based on the above factors,combined with the inertia effect on the law of gas flow in coal seams the gas to the continuity equation,motion equation,the content of equation of state for theoretical guidance,from the non steady testing technology in oil well fluid in porous medium radial basic differential equations of non steady flow principle,derived gas compression properties and gas desorption(continuity equation in the"source")under the conditions of coal seam gas radial unsteady flow of two order nonlinear partial differential equations,and the measurement of coal seam permeability The gas coefficient by using the method of the most widely(drilling radial flow method)and compared to recently proposed mathematical flow on coal seam gas radial model,the equation of state theory more closely;through the COMSOL Multiphysics numerical simulation software,combined with relevant examples of the nonlinear partial differential equations are solved,and measurement of coal seam permeability drilling the coefficient of radial flow method by comparing the analysis of inertial effect,Klinkenberg effect,gas desorption,stress,the impact of coal seam gas pressure field around the borehole distribution.