Veerle Vandeginste from the Department of Materials Engineering, KU Leuven, together with colleagues from China, has published a new article on the subject of the ion-migration effects during hydro-fracturing of deep high-salinity coal seams. The article is published in the May 2024 issue of Physics of Fluids.
Hydraulic fracturing enables effective exploitation of deep coalbed methane. During the hydraulic fracturing process, high salinity flowback fluid is generated, and this poses a significant challenge for water treatment. Therefore, we investigate the effect of hydraulic fracturing on ion migration in deep coal seams and its underlying mechanisms. In this study, nuclear magnetic resonance, inductively coupled plasma mass spectrometry, scanning electron microscopy, and energy dispersive x-ray spectroscopy were utilized to systematically study the diffusion behavior of ions and its correlation with water imbibition. Our results show that imbibition equilibrium was reached before ion diffusion finished. Ion diffusion displays three linear stages followed by a plateau part, and the second segment is the fastest one. The water–coal interactions result in the diffusion of ions into solution, with the most significant increases in Ca2+, Mg2+, Na+, K+, Li+, Cu2+, V5+, Hg2+, Pb2+, B3+, Mo6+, Cr3+, Sn4+, Cd2+, Cs+, Sr2+, and Ba2+. The dissolution of calcite, sodium feldspar, and kaolinite are the main contributions for ion migration. In addition, these reactions not only cause the release of ions into the solution but also lead to the formation of secondary pore-fractures and secondary precipitation. The results of this work help to understand better the ion migration induced by the water–coal interaction and to evaluate the fluid properties in deep coal formations.
Reference
Physics of Fluids 36, 052112 (2024) https://doi.org/10.1063/5.0206794
Acknowledgements
The authors acknowledge financial support by the National Natural Science Foundation of China (No. 42125205) and the Fundamental Research Funds for the Central Universities (Nos. 2652023001 and 2652023204).
