注CO₂增产煤层气技术（CO₂−ECBM）可以降低温室气体排放，具有清洁能源生产和环境保护的功能。为研究气−水两相流条件下，在含水煤层中注CO₂增产CH₄的排采规律以及不同初始含水饱和度、不同CO₂注入条件对CH₄产量、CO₂储存和储层渗透率的影响，构建了竞争吸附、温度变化、煤体变形以及水运移的流−固−热耦合模型，通过与现场数据、已有试验以及现有模型的数值解结果，对比证明了模型有较高的准确性并对模型的优势做出具体阐述，随后利用COMSOL开展了CO₂−ECBM数值模拟。结果表明：注CO₂可以提升CH₄产气速率和产气量，这表明了注CO₂增产的可行性。随着CO₂持续注入，储层CH₄浓度降低，CO₂浓度升高，注气井附近温度升高，生产井附近温度降低且从注气井到生产井的温度缓慢下降；注气抽采期间，水相相对渗透率逐渐减小，气相相对渗透率逐渐增大。由于有效应力、基质收缩/膨胀共同作用，储层渗透率呈现“降低—升高—降低”的趋势；煤层初始含水饱和度越大，CH₄产量越低，渗透率下降幅度越小。累计CH₄产量最大下降15.19%，忽略煤层中水的影响会高估CH₄产量，在进行数值模拟时要考虑煤层水的影响；CO₂注入温度与注入压力越大，CH₄产量越大，渗透率下降幅度越大。累计CH₄产量分别增加13.27%、39.77%，渗透率分别下降20.4%、46.14%，提高CO₂注入温度和注入压力有利于提高CH₄产量。

The technology of CO₂-enhanced coalbed methane (CO₂-ECBM) can reduce greenhouse gas emissions, and has the function of clean energy production and environmental protection. In order to study the drainage and production laws of CH₄ production by CO₂ injection in water-bearing coal seams under gas-water two-phase flow conditions, as well as the effects of different initial water saturation and CO₂ injection conditions on CH₄ production, CO₂ storage, and reservoir permeability. A coupled fluid-solid-thermal model for competitive adsorption, temperature changes, coal deformation, and water transport was constructed. The high accuracy of the model was demonstrated by comparing with the field data, existing experiments and numerical solutions of existing model, and the advantages of the model were specified. CO₂-ECBM numerical simulation were subsequently carried out using COMSOL. The results shown that, CO₂ injection can enhance the rate and amount of CH₄ production, which indicated the feasibility of CO₂ injection to increase production. With the continuous CO₂ injection, the CH₄ concentration in the reservoir decreased, the CO₂ concentration increased, the temperature near the gas injection well increased, the temperature near the production well decreased and the temperature from the gas injection well to the production well slowly decreased. Water phase relative permeability gradually decreased and gas phase relative permeability gradually increased during gas injection and extraction period. Due to the combined effect of effective stress and matrix shrinkage/expansion, the reservoir permeability exhibited a trend of “decrease-increase-decrease”. The higher the initial water saturation of the coal seam, the lower the CH₄ production and the lower the permeability decrease. The maximum decrease in cumulative CH₄ production was 15.19%. Ignoring the impact of water in coal seams can overestimate CH₄ production, and the impact of coal seam water should be considered in numerical simulation. The higher the CO₂ injection temperature and pressure, the greater the CH₄ production and the greater the permeability decrease. The cumulative CH₄ production increased by 13.27% and 39.77%, and permeability decreased by 20.4% and 46.14%, respectively. Increasing the CO₂ injection temperature and pressure was conducive to increase CH₄ production.