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基于气固耦合理论,建立了地面井预抽瓦斯的气固耦合力学模型和数值计算模型,并分析了地应力、储层压力等因素对地面井预抽瓦斯效果的影响。计算结果表明:地应力与煤层产气率之间呈现非线性负相关关系。抽采前期瓦斯的产出速率随地应力的增大而显著变小,随着抽采的进行,地应力对产出速率控制性逐渐减弱;储层压力与瓦斯产气率呈正相关关系。煤层瓦斯压力越大,初始瓦斯抽采效率越高,抽采产量越大,随着抽采时间的增加,煤层瓦斯压力下降,瓦斯抽采效率迅速降低;瓦斯产出速率由煤体渗透率和储层瓦斯压力梯度两者共同决定,抽采初期前者对瓦斯产出速率的控制性占主导地位,随着抽采的进行前者对其控制性要逐渐小于后者。
Based on the theory of gas-solid coupling, the gas-solid coupling mechanics model and numerical calculation model of pre-drainage gas for ground wells are established. The influence of ground stress, reservoir pressure and other factors on the pre-drainage effect of surface wells is analyzed. The calculation results show that there is a nonlinear negative correlation between the geostress and the gas rate of the coal seam. The output rate of gas in the early stage of gas drainage decreases remarkably with the increase of site stress. With the progress of gas drainage, the controllability of geostress to output rate decreases gradually. There is a positive correlation between reservoir pressure and gas production rate. The higher the coal seam gas pressure, the higher the initial gas extraction efficiency, the greater the pumping output. With the increase of extraction time, the gas pressure in the coal seam decreases and the efficiency of gas drainage decreases rapidly. The gas production rate is determined by the coal permeability and The gas pressure gradient in the reservoir determines both. In the early stage of gas drainage, the predominance of the former on the rate of gas output dominates, and the controllability of the former is smaller than the latter as the gas extraction progresses.