Experimental research of the surfactant effect on seepage law in coal seam water injection

Abstract

Coal seam water injection is one of the important means of mine disaster prevention, which helps to restrain the production of dust and reduce gas concentration. Ionic surfactant can change the capillary force of water in coal pore fissures, so as to enhance the wetting effect of coal seam water injection. However, the research on the effect of surfactant on the seepage process is still relatively weak. In order to explore the influence of surfactant on the seepage of coal seam water injection, the bituminous coal of Daliuta Coal Mine was used as the experimental coal sample to carry out wettability test and triaxial seepage experiment. The influence mechanism of capillary effect in the wetting and seepage stage of coal seam water injection is analyzed. The results show that the water injection process of cylindrical coal core goes through the unsaturated seepage stage and the steady seepage stage. In the process of unsaturated seepage, the increase rate of cumulative flow at the entrance of coal sample changes from fast to slow. And the instantaneous flow rate of surfactant is higher than that of water with a range of 0.1∼4 mL/min in the unsaturated seepage stage. The cumulative flow rate of water injection increased by 40%–60%. The instantaneous flow rate of water injection increases with the increase of capillary rising factor, and the correlation coefficients is 0.977. While in the stable seepage stage, the cumulative flow basically shows a linear increasing trend, and the increasing percentage of cumulative flow of water injection is lower than that of unsaturated seepage. It indicates that the surfactant can significantly improve the wetting rate at the stage of unsaturated seepage, and surfactants enhance the ability of liquid-solid interface to replace gas-solid interface.