Study On Creep-Seepage Law Of Heterogeneous Coal Under Temperature And Stress

The injection of coalbed methane gas(gas)as an emerging technology for increasing production of coalbed methane has attracted wide attention at home and abroad due to its high feasibility.There have been many studies on coalbed methane gas injection.However,in these studies,most of them focus on heat injection to promote coal gas desorption and gas seepage,and the gas containing coal as an elastomer to calculate,ignoring temperature and stress for gas containing coal The effect of the change and the change in its permeability.In this paper,we study the gas-bearing coals under different temperature and stress as the research object,and study the gas seepage law in the creep process of coal under thermal coupling conditions.We first establish the static equilibrium equation of gas containing gas,the three-dimensional creep equation of gas-containing coal considering the temperature influence and the seepage field equation.Through these equations,we finally establish the creep-seepage mathematics model of gas-containing coal.Then we pass the physical test to measure the relevant parameters of the coal body;at the same time,after processing the relevant data,the fitting function(volume modulus K1 ?K2,and viscosity coefficient ?)related to the mechanical parameters of the coal isobtained.Using the relevant parameters of gas containing coal,the software was used to simulate the creep deformation process of gas containing coal and its permeability.At the same time,the influence of the heterogeneity of gas-containing coal on the test results is also considered.The random modulus E and initial porosity n0 of the gas-containing coal are established by using the random function rn1(x,y,z)in the software.Through the analysis of the simulation test results:(1)the increase of temperature and the increase of axial stress,not only the initial volume strain of the coal containing gas is increased,but also the volumetric strain increment of the decelerating creep phase and the stable creep phase.It also becomes larger and the creep deformation rate is faster.(2)The increase of the effective stress and the temperature of the gas-containing coal will cause the initial permeability to decrease to a certain extent,and the permeability loss rate will also increase.(3)It can be found through an intuitive image that the number or smoothness of effective seepage pores is reduced during the creep process of heterogeneous coal.