煤层气井排采过程中煤粉运移规律研究

Migration patterns of coal powder in coal reservoirs during the well drainage

研究煤粉运移规律并以此制定减少煤粉产出的措施是保证煤层气井高产、稳产的关键。基于煤粉颗粒在煤岩通道中的运动学和动力学分析,建立了煤储层中煤粉随流体运移的数学模型,并依据现场调研资料研究煤粉粒径、通道孔径等因素对煤粉运移的影响。实例分析结果表明,煤储层中煤粉颗粒运移的临界流速表征了煤层气井开始产出煤粉的特征值,当流体流速达到临界流速时煤粉即发生运移。随煤粉颗粒和通道(喉道)半径不断减小,煤粉运移临界流速逐渐降低,颗粒更容易运移,将加重煤层气井的煤粉产出量。骨架煤粉颗粒的增大和相邻颗粒质心连线与通道方向间夹角的减小使得通道孔壁变得更加粗糙,煤粉运移临界流速逐渐提升,这会减轻煤层气井的出煤粉问题。该研究首次系统而定量的分析了煤储层中煤粉运移规律,为控制煤层气井出煤粉量和采取合理的排采作业方法提供了重要依据。

The study on the transport patterns of coal powder the formulation of measures to reduce the output of coal powder are the key for the high and stable productivity of coalbed methane(CBM) wells. Based on the kinematic and dynamic analysis of coal particles in coal reservoir channels, the mathematical model of coal moving with liquid was developed. And the effects of coal powder size and channel radius on coal powder migration were analyzed based on the data of site investigation. The results show that the critical flow rate for coal particle characterizes the eigen values of coal powder produced from CBM well. The coal particle moves while its flow rate reaches to the critical value. With the progressive decrease of the size of powder and channel radius, the critical flow rate of powder coal migration decreases gradually, and coal particles move more easily, the output of powder coal of CBM well will increase. The increase of coal powder size and decrease of angle α between centroid connection and channel lead to rougher channel wall and higher critical flow rate. The critical flow rate of powder coal migration increases gradually, reducing the output of coal powder in CBM well. The systematic and quantitative analysis of coal powder migration in coal reservoir was completed for the first time, which will provide the reasonable basis for controlling the output of powder coal in CBM well and adopting the reasonable operating methods of gas drainage and extraction.