Experimental Investigation of CS₂ Extraction to Enhance the Permeability of Coal

To examine the permeability enhancement effect of the carbon disulfide (CS ) extraction on block coal samples, in this study, different cylindrical samples of anthracite coal were selected to conduct CS extraction experiments. Comprehensive measurement techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, low-temperature nitrogen adsorption, industrial computed tomography, and permeability measurements, were employed to analyze the variations of in the chemical structure, microcrystalline structure, pore–fracture structure, and coal permeability before and after the CS extraction treatment. The results showed that CS extraction can improve the connectivity of multi-scale migration channels, with which the coal permeability can be enhanced. Also, it was found that the permeability enhancement performance by the CS extraction is related to the coal anisotropy, as the coal permeability in the vertical bedding direction is smaller than that in the parallel bedding direction before and after CS extraction. Also, the CS extraction had a time effect on enhancing the coal permeability, and the permeability enhancement was more significant after a longer period of CS treatment. It can be predicted that the permeability can be enhanced up to more than 1 mD when the extraction time exceeds 6 h. Also, we concluded that CS fracturing is worth exploring by the on-going studies to enhance the permeability and CBM recovery in low-permeability reservoirs. 2 2 2 2 2 2 2 2 2