煤储层排采液流携粉运移模型与产出规律

基于液固两相流理论建立煤层液流渗流数学模型,并给出描述煤岩产气通道流动状态的偏微分方程和煤层液流携粉运移特征的数学模型,依据数值求解结果分析产气通道中的液流压力和流速以及煤粉随液流运移的浓度分布情况。结果表明,煤储层近井区域液流高流速状态使得通道液流中的含煤粉量达到最高值,排采初期较大的排液量和压差波动使得其煤粉产出较多,而稳产阶段的产液量减小且煤储层与井底间的生产压差降低使得通道中煤粉浓度较低,生产压差由2.05 MPa提高到3.05 MPa后,产气通道各节点最大含煤粉量由0.112%迅速升至0.608%;且稳产阶段煤层泄流体产气通道孔径的增大,会进一步降低通道中煤粉浓度,产气通道高度由0.30 mm扩大到0.90 mm,产气通道各节点最大含煤粉量则由0.759%降至0.160%。该算法提出煤储层泄流体煤岩产气通道管流的概念并定量描述排采液流携煤粉运移的特征,为准确预测煤层气井排采中的煤粉产出情况和制定合理的防煤粉措施提供了依据。

Migration models of pulverized coal flowing with fluid and its production in CBM channels for the coal reservoirs

The mathematical models of fluid mechanism in porous medium was developed based on the two phase liquid+solid flow theory.Then the pulverized coal migration flowing with fluid was established for coalbed methane (CBM) channels in coal reservoirs.The pressure and velocity of fluid flow and coal concentration were given out based on numerical solution.The results show that the maximum coal concentration results with high fluid flow rate are near wellbore.The coal production in CBM channels is high due to the high water flow rate and pressure drop during the initial production.However,it is low resulted with the reduced water production and pressure drop between coal reservoir and bottom hole during the resistant period.The maximum coal concentration increases from 0.112% up to 0.608% when pressure drop is from 2.05 MPa to 3.05 MPa.And the enhanced diameters of CBM channels are beneficial to the decrease of coal concentration.The increased diameter of channel from 0.30 mm up to 0.90 mm leads to the decreased coal concentration from 0.759% to 0.160%.The pulverized coal migration flowing with fluid is predicted accurately in CBM channels,which will provide the reasonable basis for calculating coal production and designing coal control.