题 目： Cryogenic Treatment of Coal and Its Application in CBM and Coal Mine Gas Control
主 讲 人：Dr. Shimin Liu
工作单位：Department of Energy and Mineral Engineering, the Pennsylvania State University, USA
时 间：At 3:00-4:30 p.m., June 3, 2019
地 点：School of Resource & Environment and Safety Engineering Academic Report Hall (the first floor of Fourth Building)
Shimin Liu is an Associate Professor of Energy and Mineral Engineering at Penn State University and he holds Ph.D. degree in Engineering Sciences from Southern Illinois University. His research interests include flow of fluids in porous media (with application to gas flow in coal/shale, coalbed methane reservoir engineering, gas shale reservoir engineering, carbon sequestration in geologic media and abandoned coal mines); imaging (micro-X-ray computed tomography, synchrotron X-ray scattering, neutron scattering/diffracting, scanning/transmission electron microcopy) and analysis to study physical structure of rocks; flow-induced micro-structuring of rocks; geomechanical responses of unconventional reservoirs with depletion. As PI, he has successfully secured funding from various US federal agencies, including US Department of Energy, US National Science Foundation, CDC-NIOSH, Alpha Foundation, SME Foundation and industrial partners with total of external grant with over 3 million US Dollars. Out of his research, he has published more than 90 peer-reviewed journal publications and with ~1500 citations. Right now, he is editor-in-chief for International Journal of Coal Science and Technology. For more details, please refer to his personal web at Penn State at https://www.eme.psu.edu/directory/shimin-liu。
Fracturing using liquid nitrogen (LN2) has been successfully applied in coalbed methane reservoirs stimulation in field since the 1990s. However, the mechanism of LN2 acting on the alteration of pore structure is still obscure. For moisture coal, the cryogenic treatment can provide both frost-heaving force and the expansion force to increase the pore volume and fracture aperture and density. Investigation on the evolution of pore structure predominately provides deep understanding of the CBM performance after cryogenic stimulation and potentially optimizes the fracturing plan in field. This study used the particle method to examine the change in pore structure due to LN2. The particle method eliminates the pre-existing fracturing network and ensures the transport of gas is purely driven by diffusion. In this study, we focus on the micro-pore modification by LN2 treatments. The coal particles were treated by LN2 immersion. The adsorption experiment was conducted to measure the sorption and diffusion behavior of coal. The results indicated that the micropore volume increased by LN2 treatments and thus sorption capacity and diffusion coefficient of coal were improved. This study provides a scientific justification for diffusion improvement and gas production enhancement for high “sorption time” CBM reservoirs.