Impacts of ionic surfactants on water seepage in coal fractures

To optimize the selection of surfactants for coal seam water injection, this study examines the effects of ionic surfactants (DTAB and SDS) on water seepage in low-rank long-flame coal. A three-dimensional Eulerian two-phase flow model is established via ANSYS Fluent software to simulate the surfactant migration and is then validated through triaxial seepage experiments. The following crucial results are obtained: For long-flame coal from Houwenjialiang Coal Mine in Ordos City, Inner Mongolia Autonomous Region, China, the seepage coefficient increases with higher water injection pressure when using two surfactant solutions. Subjected to the water injection pressure of 2 MPa, the seepage coefficients of SDS and DTAB surfactants in order are obtained as 0.06 and 0.08, respectively, and the enhancement effect of cationic surfactant DTAB on coal seam water injection is superior to that of anionic surfactant SDS. In the presence of external pressure, the liquid seeps upwards along the pressure direction and with a steady flow, and seeps around along the pores and cracks of the coal body. The obtained results also reveal that the adsorption effect of SDS surfactant on coal is strong, resulting in a weaker water injection effect with increased water injection time into the coal seam.