煤层气多层合采是提高单井产量的重要手段，但开发实践表明煤层气合采效果与控制因素复杂多变，面临产气贡献判识、产气潜力预测、产层组合优化等技术难点。不同煤储层解吸产气的叠加性决定着煤层气合采能否取得高产。

提出解吸次序判断、解吸区间叠加性与解吸阶段匹配性分析、井控可解吸量预测的煤层气合采解吸叠加效应分析方法，并以黔西小屯井田为例开展应用研究。

结果表明，该区煤储层具有吸附能力强、含气饱和度低、临界解吸压力低的特点。煤层气产层可划分为2套解吸系统，上部解吸系统的解吸次序为6_上、7、6_中与6_下煤，下部解吸系统的解吸次序为34、33煤。以生产过程动液面变化为刻度，分析煤层气合采过程中各煤层的解吸历程，发现6_上、7、6_中、6_下煤在45 m的动液面范围内能够同步解吸，33煤与34煤在92 m的范围内能够同步解吸。基于等温吸附曲线揭示各煤层解吸阶段的匹配性，由于临界解吸压力低，各煤层解吸后直接进入敏感解吸阶段，解吸效率高且匹配性好，有利于高产，但存在压降空间不足，排水周期长等弊端，对煤储层改造和排采提出更高要求。井控可解吸量及其时变曲线预测表明，当解吸系统内部所有产层同步解吸时，将迎来解吸高峰，此阶段上部系统井控可解吸量378.09万 m³，日均4.20万m³，下部系统井控可解吸量199.11万m³，日均1.08万m³。上下2套解吸系统均显示了良好的解吸叠加效应，分别构成两套有利合采产层组合。该方法可为煤层气合采产气贡献识别、产气潜力预测与产层组合优化提供参考依据。

The commingled production of coalbed methane (CBM) serves as a significant means to increase single-well production. However, production practices reveal that the commingled production of CBM exhibits complex and varied effects and controlling factors, facing technical challenges of identifying gas-producing contributions, predicting gas-producing potential, and optimizing pay interval combinations. The superposition of desorption for gas production among different coal seams determines whether high CBM production can be achieved using commingled production.

This study proposed an analytical method for the desorption superposition effect in the commingled production of CBM, involving determining desorption sequences, analyzing the superposition of desorption intervals and the matching of desorption stages, and predicting well-controlled desorption capacities. The proposed method was applied to the Xiaotun mine field in western Guizhou Province, China.

The results indicate that coal reservoirs in the Xiaotun mine field feature high adsorption capacities, low gas saturation, and low critical desorption pressures. The CBM pay intervals can be categorized into the upper and lower desorption systems. The upper desorption system manifested a desorption sequence of the No.6 upper, No.7, No.6 middle, and No.6 lower coal seams, while the lower desorption system displayed a desorption sequence of the No.34 and No.33 coal seams. Using changes in the working fluid during the production process as an indicator, this study analyzed the desorption processes of coal seams during the commingled production of CBM. The analytical results reveal that the synchronous desorption of the No.6 upper, No.7, No.6 middle, and No.6 lower coal seams can be achieved within a working fluid of 45 m and the synchronous desorption of the No.33 and No.34 coal seams can be gained within a working fluid of 92 m. Isothermal adsorption curves discovered the matching of the coal seams' desorption stages. The low critical desorption pressures allowed various coal seams to directly enter the sensitive desorption stage after desorption, suggesting high desorption efficiency and effective matching. This creates favorable conditions for high CBM production. However, limitations like insufficient pressure drop space and long drainage periods impose high requirements for coal seam stimulation and CBM production. The well-controlled desorption capacities and their time-varying curves indicate that gas desorption capacities peaked in the case of the synchronous desorption of all pay intervals within the respective desorption systems. In this case, the upper and the lower desorption systems yielded well-controlled desorption capacities of 378.09×10⁴ m³ (daily average: 4.20×10⁴ m³) and 199.11×10⁴ m³ (daily average: 1.08×10⁴ m³), respectively. Both desorption systems demonstrated satisfactory desorption superposition effect, each forming a favorable pay interval combination for the commingled production of CBM. The proposed method will provide a reference for identifying gas-producing contributions, predicting gas-producing potential, and optimizing pay interval combinations for the commingled production of CBM.