Characteristics of seepage of microemulsions in coal

Abstract

In order to improve the permeability of coal seams, Microemulsions (MEs) are used as seepage reagents and their effect is compared with those of distilled water and Sodium Dodecyl Sulfate (SDS) solution. For comparison, the seepage time and permeability of different seepage reagents are measured by a seepage apparatus. Furthermore, the scanning electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy and contact angle measurement approach are adopted to explore the seepage characteristics of MEs. The results show that MEs take less time than the SDS solution and distilled water for the seepage flow to reach 1 ml, and that MEs have a higher permeability in coal than the SDS solution and distilled water. The reason is that the MEs treated coal has better pore connectivity than the SDS solution treated, water treated and raw coal because its effective seepage pores are enlarged and increased. Moreover, MEs can reduce the content of montmorillonite, and thus reduce the blocking volume in seepage pores. In addition, MEs can increase the oxygen-containing functional groups, and their contract angle with the coal surface is smaller than that of SDS solution and distilled water. Therefore, MEs have better wettability than the SDS solution and distilled water since they can be easily spread on the coal surface and in coal seam pores. As a consequence, they can wet the coal pore wall more easily during seepage, thus reducing the difficulty of the seepage and migration of MEs and enhancing the seepage effect. Therefore, this study on MEs is of great significance to coal seam water injection in deep mining.