Study On Energy Distribution Law Of Coal Seam Gas Injection In Low Permeability Reservoir

The heat injection of coal seam gas in low permeability reservoir is one of the effective ways to increase the production of coal-bed methane in the future,and the energy distribution law after energy injection into low permeability reservoir determines the economy and feasibility of heat injection in low permeability reservoirs.In order to obtain the energy distribution law of coal seam gas injection in low permeability reservoir,this paper uses the method of experimental research,theoretical analysis and numerical simulation to obtain the experimental relations between the porosity of coal body,the permeability of coal body,the desorption amount and temperature of coal-bed methane,and establishes the dynamic theoretical model of the desorption heat and desorption of coal-bed methane.And combining the theories of thermodynamics,heat transfer,seepage mechanics and geotechnical mechanics,this paper establishes the mathematical model and heat flow distribution model of hot-flow-solid coupling in coal seam gas injection of low permeability reservoir,and uses COMSOL Multiphysics software to simulate the engineering example numerically.The microstructure observation of coal body hole fracture under the action of temperature shows that the porosity of coal body increases exponentially with the increase of temperature.The experiment of coal body permeability under different temperature and stress shows that the permeability of coal body has a transition zone,low stress zone,with the increase of temperature,the permeability of coal body increases gradually,in high stress zone,with the increase of temperature,the permeability of coal body decreases.The experiment of coal seam gas desorption under different temperature and stress shows that the desorption rate of coalbed methane increases with the increase of desorption temperature,the total output is increased,the correction formula of coalbed methane desorption power is established as (?) and the desorption dynamic coefficient beta?is proposed.The results of coal bed methane desorption heat test show that the desorption heat required for the desorption process of coalbed methane increases exponentially with the increase of desorption quantity,and the relationship between the desorption heat and desorption quantity of coalbed methane conforms to the exponential function:(?);The simulation results show that with the increase of heat injection time,the heat absorption of coal seam appears slowly and increases first,then increases rapidly,and finally reaches a stable value,the adsorption gas absorbs heat is the trend of rapid increase first,then plummeting,and then slowly rising;the desorption heat of coalbed methane is increased first slowly,then increases rapidly,and finally stabilizes;In the range of simulated examples,increasing the inlet temperature and increasing the spacing of wells can strengthen the heat transfer effect in coal reservoirs and improve the cumulative gas yield of coalbed methane.The paper has 38 figures,13 tables,95 references.