氧化处理缓解煤岩储层煤粉堵塞损害实验

为了优化煤层气井的压裂排采效果，以贵州织纳区块上二叠统龙潭组16号煤层煤岩为研究对象，开展了粉状煤样的NaClO溶液浸泡实验和柱状含裂缝煤样的NaClO溶液驱替实验，并且利用激光粒度分析、红外光谱测试及Zeta电位测试等手段，评价了NaClO解除煤岩天然裂缝中煤粉堵塞的效果，分析了氧化液与煤粉的反应机制，进而揭示了煤岩氧化解堵增渗机理。研究结果表明：①NaClO溶液对煤岩有机和无机组分具有明显的溶蚀效用，并且浓度越高，对煤粉的溶蚀率越高、“物质净移除”效果越好；②浓度分别为0.1%、1.0%的NaClO溶液可以有效解除煤粉在压裂液中的聚集，使其在压后排采过程中易于被排出；③经过NaClO溶液的氧化作用后，煤粉粒径降级，压裂液浸泡后引起的煤岩基块和煤粉吸水膨胀损害将得到有效的缓解，并且煤粉粒径越大，粒径降级率越高，浓度为1.0%的NaClO氧化液对煤粉粒径的降级效果为最佳；④经过浓度为1.0%的NaClO溶液氧化后，含裂缝煤样的渗透率可提高4.22倍，增渗效果明显。结论认为：①氧化液能够溶蚀煤粉和缝面煤岩组分、改变煤粉及缝面物理化学性质、解除煤粉颗粒聚集、促使已发生膨胀的煤粉粒径降级，进而加快已形成堵塞的煤粉的排出进程；②氧化处理有望成为煤岩储层解堵改造的一种新技术。

Experiment of relieving coal dust blockage damage in coal reservoirs by oxidation treatment

In order to optimize the fracturing production effect of coalbed methane wells, this paper performs NaClO solution immersion experiment on pulverized coal samples and NaClO solution displacement experiment on cylindrical fracture-containing coal samples by taking the coal samples taken from No.16 coal seam of Upper Permian Longtan Formation in the Zhina Block of Guizhou as the research objects. Then, the effect of NaClO on removing pulverized coal blockage in natural fractures of coal rocks was evaluated by means of laser particle size analysis, infrared spectroscopy and Zeta potential test, and the reaction mechanism of pulverized coal in oxidation solution is analyzed. Finally, oxidation, blockage removal and permeability increase mechanism in coal rocks are revealed. And the following research results were obtained. First, NaClO solution has an obvious dissolution effect on organic and inorganic components of coal rock. The greater the concentration of NaClO, the highter the dissolution rate of pulverized coal and the better the effect of “net material removal”. Second, NaClO solutions with a concentration of 0.1% and 1.0% respectively can effectively relieve the aggregation of pulverized coal in fracturing fluid, so that it can be discharged easily in the process of production after fracturing. Third, after pulverized coal is oxidized in NaClO solution, its particle size is degraded and the swelling damage of coal rock block and pulverized coal caused by immersion of fracturing fluid will be effectively alleviated. The larger the particle size of pulverized coal, the higher the degradation rate of particle size. And NaCl oxidation solution with a concentration of 1.0% is the best in the degradation effect on the particle size of pulverized coal. Fourth, after a fracture containing sample is oxidized in the NaClO oxidation solution with a concentration of 1.0%, its permeability can be increased by 4.22 times, indicating remarkable permeability increase effect. In conclusion, oxidation solution can dissolve the compositions of pulverized coal and coal on fracture surface, change the physical and chemical properties of pulverized coal and fracture surface, relieve the aggregation of pulverized coal particles, and promote the particle size degradation of expanded pulverized coal, so as to accelerate the discharge of pulverized coal which has formed blockage. In addition, oxidation treatment is expected to be a new technology for blockage removing stimulation of coal reservoirs.