查明气/水两相驱替不同粒径煤粉引起的煤中裂缝导流衰减特征对煤层气井排采时气/水两相流阶段防煤粉措施的制定意义重大。采用自制的气-液-固三相驱替煤粉模拟装置，进行了气/水两相驱替不同粒径(40~60,60~80,80~100,100~150,150~200,＞200目)煤粉在树脂-煤芯柱样裂缝中的运移实验，通过对比无煤粉气/水两相驱替的空白实验，分析了驱替不同粒径煤粉时气、水的渗流规律差异。基于气/水两相驱替不同粒径煤粉的渗流模型，结合平板理论、拟合得到的气相渗透率与裂缝缝宽的关系，定量描述了驱替过程中气体流动、液体流动、煤粉封堵所占据的裂缝缝宽随驱替时间的变化规律，并以气体、液体流动所占裂缝缝宽之和的变化规律表征了树脂-煤芯柱样裂缝导流能力的衰减特征。结果表明:在几乎相同初始驱替压力下，气、水两相通过树脂-煤芯柱样时会相互争抢柱样内裂缝空间，且气相渗透率、液相渗透率随时间变化呈三角函数分布;不同粒径煤粉驱替前期，柱样气相渗透率、液相渗透率仍会表现出管弦状波动特征，但在煤粉堵塞一定程度后，二者开始同时减小;气/水驱替不同粒径煤粉时产出液内煤粉质量浓度、裂缝完全堵塞时间随煤粉粒径减小而增大;气/水驱替不同粒径煤粉时裂缝导流能力变化可分为液体产出前的裂缝快速封堵、气/液携粉产出的裂缝缝宽小幅增加、液体流动能力骤减的裂缝快速闭合、气体流动能力缓慢降低的裂缝完全封堵等4个阶段

Finding out the variation characteristics of fracture diversion capacity in coal caused by different particle sizes pulverized coal driven by gas and water is of significance for the formulation of pulverized coal control measures during gaswater twophase flow in coalbed methane wells.Using the selfmade gasliquidsolid threephase displace pulverized coal simulation device,the experiments on the migration of different particle sizes pulverized coal (40-60 mesh,60-80 mesh,80-100 mesh,100-150 mesh,150-200 mesh,greater than 200 mesh) drived by gaswater twophase flow was carried out.By comparing with the blank experiment of no pulverized coal gaswater twophase displace,the difference of gas and water seepage law when the different particle sizes pulverized coal was driven by gaswater twophase flow was analyzed.Based on the gas and water percolation model under different particle sizes pulverized coal driven by gaswater twophase flow,combining the theory of plate,the fitting formula of the gas permeability and crack width to quantitatively describe the gas flow and liquid flow and pulverized coal block occupying crack width changing with the displace time in the displace process,the fracture diversion capacity attenuation characteristics of resincoal core sample were characterized by the variation of the crack width occupied by gas and water.The results show that under almost the same initial displace pressure,the gas and water compete with each other for the crack space in the resincoal core sample,and the gas permeability and liquid permeability change with time in a trigonometric distribution.In the early stage of pulverized coal displacement with different particle sizes,the gas permeability and liquid permeability would still show the characteristic of trigonometric distribution,after a certain degree of pulverized coal blockage,both of them start to decrease.When different particle sizes pulverized coal driven by gaswater twophase flow,the mass concentration of pulverized coal in the produced liquid and the time of crack complete plugging increase with the decrease of pulverized coal particle size.When different particle sizes pulverized coal driven by gaswater twophase flow,the change of fracture conductivity can be divided into four stages:rapid sealing of fracture before liquid production,small increase of fracture width of gas and water carrying pulverized coal out,rapid closing of fracture with sharp decrease of liquid flow capacity,and complete sealing of fracture with slow decrease of gas flow capacity

1 实验材料与研究方法

    1.1 实验材料与主要仪器

    1.2 研究方法及测试步骤

2 实验结果与分析

    2.1 无煤粉驱替时气、水通过树脂-煤芯柱样的渗流特征

    2.2 气、水驱替不同粒径煤粉时渗流特性

    2.3 树脂-煤芯柱样内裂缝导流衰减特征定量分析

3 结论