煤层气解吸机理数值模拟研究

NUMERICAL SIMULATION RESEARCH ON COALBED METHANE DESORPTION MECHANISM

针对不同饱和类型煤层的特点及临界解吸压力在地层压力上升、下降过程中的不同作用,建立了煤 层气解吸过程的数学模型。模型能够反映气体解吸的真实情况。利用此数学模型,编制了计算程序,通过实例,计 算分析了煤层气解吸的主要机理:超饱和煤层是游离气和气体解吸的累加作用;饱和、欠饱和煤层在开采过程中控 制区域内两相区逐渐扩大;欠饱和煤层高于临界解吸压力的区域没有解吸,造成产量低下。

A numerical model of coalbed methane desorption course was set up in consideration of the characteristics of the coal beds with different saturation types and the different actions of critical desorption pressure on formation pressure rising and dropping. The model can reflect the actual circumstances of methane desorption. Through calculating and analyzing a case on the basis of developing the computional program, it was concluded that the supersaturated coal beds resulted from the accumlation of free methane and desorbed methane; the two-phase area was gradually enlarged in the course of methane production from the saturated and undersaturated coal beds; and the methane desorption couldn't be carried out in the undersaturated coal beds at the areas where formation pressure is higher than critical desorption pressure, thus causing the low methane production.