近井部位压裂裂缝内微粒运移与堵塞是煤层气井减产的重要因素之一.客观查明近井压裂裂缝内充填特征规律与堵塞机制对气井解堵理论深化、解堵工艺改进非常关键.基于煤矿掘进工作面开挖观测现象,对沁水盆地南部煤层气直井近井压裂裂缝内充填特征与裂缝堵塞机制进行系统分析.结果表明:煤层气井近井压裂裂缝内充填物由煤粉、支撑剂及完井滤饼组成;完井滤饼对压裂裂缝启裂、延展及支撑剂分布具有关键控制作用,近井裂缝壁面完井滤饼能够减缓压裂液的滤失速率,但在滤饼尖灭位置压裂液滤失速率突然增大时极易脱砂形成脱砂楔体,楔体在流体冲击下压实致密,排采期气液两相流携带煤粉流经脱砂楔体时卡在砂粒间形成裂缝堵塞;基于颗粒堆积模型与黄金过滤原则,针对研究区粒度中值0.045 mm的煤粉,脱砂楔体处注入支撑剂粒径大于0.900 mm可降低裂缝内煤粉堵塞程度.%Particle migration and blocking in fracturing fractures near wellbore area can be one of the important factors to pro-duction reduction of coalbed methane ( CBM) wells. It is essential to reveal the filling characteristics and plugging mecha-nism of fracturing fractures in order to remove the plug and increase production. In this study, based on the in-site observa-tions of the fractures appeared in tunnels of underground coal mines, the filling characteristics and blocking mechanisms in the fractures of vertical CBM wells in southern Qinshui Basin were investigated. The observation shows that the fillings con-tain coal fines, proppant and well completion filter cake in the fractures near wellbore. Completion filter cake can control the initiation and propagation of fractures, and proppant distribution, and it can reduce the filtration rate of fracturing fluid. But when the fluid flows through the location where the filter cake is pinched out, significant fluid-loss can occur, which can take off sands and form sand wedge, and further the wedges become compacted and filled with coal fines carried by gas-liquid phase flow, then blocking or plugs of the fractures can be formed, reducing the flow capacity of the fracture seriously. It pro-poses that, based on a particle gathering model and the golden filtration principle, the size of proppants used in fracturing should be greater than 0. 900 mm in order to reduce the plugging coal fines with median size of 0. 045 mm that found in the study CBM area.
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