Experimental Study On Coal Seam Gas Displacement By Water Flooding Under Different Conditions

On the basis of the research status of coal seam water flooding and gas displacement at home and abroad,the micro mechanism of coal seam water flooding gas displacement is analyzed and summarized.The adsorption-water injection-displacement experiment device designed by the school was used to carry out the experimental study on the coal seam water flooding and gas displacement under different conditions,and combined with the underground coal seam injection test,it was verified that the coal seam injection promoted the underground gas drainage.The influence mechanism of coal seam water injection on gas drainage under different conditions is analyzed and explained.The experimental results show that with the increase of water injection pressure,the amount of water flooding displacement of coal seam also increases,and with the increase of adsorption equilibrium pressure,the amount of water flooding displacement of coal seam also increases,and the lower the degree of coal metamorphism,the easier it is to drive gas.The critical size of the water solution permeating to the coal sample decreases,and the gas with smaller pore size can be effectively driven by the water solution.Based on the experimental study of coal seam flooding displacement gas under different conditions,the coal seam water flooding displacement gas can be divided into three stages,namely,the early stage,the middle stage and the end stage of the displacement.Through the analysis of the microscopic mechanism before and after injection of coal seam,the mechanism of water solution to gas displacement is embodied in the drive of large pore diameter and the capillary force of small pore size.Absorption displacement and competitive adsorption in micro pores are three aspects.