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通过分析煤层气吸附特点,在液相吸附理论基础上描述了煤层气复合解吸过程。对于初始状态具自由气的煤层,建立了考虑液相吸附及复合解吸的水侵气藏物质平衡方程,并利用气藏A压力对其进行线性化。气藏A压力与H压力下的生产指示曲线差值即煤层气的解吸气量。同时,对于初始状态下没有自由气的煤层气藏,根据King方法建立了考虑复合解吸作用的煤层气物质平衡通式。实例计算表明:该煤层气的物质平衡回归直线过原点,说明在初始状态下并没有自由气;复合解吸下的物质平衡直线斜率较气相吸附的回归直线小,复合解吸对产量的影响更大;复合解吸作用会降低煤层气的可采储量。
By analyzing the characteristics of coalbed methane adsorption, the complex desorption process of coalbed methane is described based on the theory of liquid phase adsorption. For coal seam with free gas in the initial state, a material balance equation of water infiltration reservoir considering liquid phase adsorption and compound desorption was established, and linearized by A pressure of gas reservoir. Gas reservoir A pressure and H pressure under the production indicated that the difference between the desorption of methane gas. Meanwhile, for CBM reservoirs with no free gas in the initial state, the general formula for the CBM balance considering recombination and desorption was established according to King’s method. The case study shows that the material balance of CBM regresses linearly across the origin, indicating that there is no free gas in the initial state. The slope of the material balance line under compound desorption is smaller than the regression line of gas adsorption, and the effect of compound desorption on the yield is greater. Combined desorption can reduce recoverable reserves of CBM.