Experimental Study on Migration and Intrusion Characteristics of Pulverized Coal in Propped Fractures

Abstract

Aiming at the problem of pulverized migration and plugging propped fractures during coal seam fracturing, we experimentally studied the pressure changes and pulverized coal blocking characteristics with deionized water and solutions of three surfactants including 1227 (C21H38ClN), SDS (C12H25SO4Na) and TX-100 (C34H62O11). A device capable of visualizing propped fractures was established, and simulation experiments were conducted with solutions of different surfactants at different injection flow rates. The obtained images were binarized and analyzed to quantify the pulverized coal blockage degrees of facture under different conditions. The experimental results show that: (1) The higher the injection flow rate, the higher the inlet pressure. (2) All three surfactants can lower the injection pressure, as compared with water alone. SDS decreases the injection pressure more obviously at low injection flow rates, and the other two perform better at high injection flow rates. (3) Similar to their effects on inlet pressure, the ratio of pulverized coal in SDS solution is lower at low injection flow rates, while TX-100 and 1227 solutions show lower ratios of pulverized coal at high injection flow rates. Our work has provided a theoretical support for coal blockage removal and pressure reduction in propped fractures during coal seam fracturing to improve coal seam permeability and further improves the dust prevention effect of coal seam water injection.