煤粉集合体的团聚-分散效应对支撑裂缝导流能力作用机制研究

煤粉多以集合体状赋存，其粒径跨度大且动态变化，在煤层气生产中产出较为普遍，易造成压裂支撑裂缝速敏伤害和卡泵埋泵现象。随着煤层埋深和地应力增加，煤粉集合体团聚-分散效应对排采中支撑裂缝导流能力的影响越发显著。本项目拟通过对比沁水盆地矿井下原位样品和地面煤层气井产出煤粉特征，确定煤粉集合体成因与类型；采用扫描电镜、XRD、XPS、Zeta电位和激光粒度分析等测试手段，分析煤粉集合体在KCl压裂液中团聚-分散效应。通过选优表面活性剂改善煤粉集合体的团聚-分散行为，结合吸附性、官能团和电动电位综合研究其团聚-分散机理。以“KCl溶液-表面活性剂-煤粉”分散系作为流体介质，利用自主研发的可视化煤粉运移模拟装置开展支撑裂缝中煤粉流动实验，构建煤粉集合体在团聚和分散不同状态下运移的力学模型，以及定量分析其在受限的支撑裂缝空间中的阻流机制。研究成果能够为煤粉稳定剂的优选和排采制度的优化提供依据和指导。

Coal fines are mostly in the form of aggregates with a wide particle size span and dynamic particle size. It is common to produce coal fine aggregates during the drainage of coalbed methane, which leads to the damage of velocity sensitivity on the propped fractures, pump stuck and buried. With the increase of coal seam buried depth and in-situ stress, the reunion-dispersion effect of coal fine aggregates and its influence on the propped fracture conductivity in drainage are more significant. This project intends to determine the causes and types of coal fine aggregates by collecting and comparing in-situ samples from underground mines and coalbed methane wells on the ground in Qinshui Basin. By means of X-ray diffraction, X-ray photoelectron spectroscopy, Zeta potential and laser particle size analysis, the controlling factors of reunion-dispersion effect of the samples with different types in simulated fracturing fluid (KCl solution) are illustrated. Furthermore, the surfactants are optimized to improve the reunion-dispersion effect of the coal fine aggregates, and the surface modification mechanism is studied from the perspective of adsorption, functional group and electromotive potential. On these basis, the dispersion systems of “KCl solution - surfactant - coal fines” are used as the fluid medium, and the self-developed coal fines migration simulation device is used to investigate the coal fines flow in the propped fracture, so as to construct the mechanical model of coal fine aggregate migration in different states of agglomeration and dispersion, and quantitatively analysis the flow resistance mechanism in the confined propped fracture space. The research result can provide basis and guidance for the optimization of coal stabilizer and drainage system.