Abstract
Gas diffusion in a porous medium is a very complex process. Aiming at accurately describing the whole process of gas diffusion in a coal particle, a dynamic diffusion model of capillary pores in a coal particle (hereafter referred to as CPCPDD model) which is dependent on both the pore size and the pore pressure and based on the fractal characteristics of these capillary pores was established according to the characteristics of gas diffusion in different-sized pores. Next, parameters of the CPCPDD model were obtained through gas desorption, low-temperature nitrogen adsorption and mercury injection experiments on a coal particle. Furthermore, a comparative analysis was made between the solution results of the CPCPDD model and the data obtained from the gas desorption experiment. The results suggest that the CPCPDD model proposed in this study can accurately describe the whole process of gas diffusion in a coal particle. The diffusion coefficient obtained by the CPCPDD model is a variable related to the pore diameter and the pore pressure, and the classical uni-pore diffusion model, bi-disperse diffusion model and the multi-pore diffusion model are specific manifestations of the CPCPDD model in different pore size ranges. The research results boast crucial theoretical significance for in-depth understanding and interpretation of gas migration in coal reservoirs.
Article Highlights
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1.
A new dynamic diffusion model for capillary pores in coal particle is established in this paper.
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This new model is based on the high-pressure mercury injection experiment and low-temperature nitrogen adsorption experiment.
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This new model could accurately describe the whole process of gas diffusion in a coal particle.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (51974109, 42002185), the Program for Leading Talents in Scientific and Technological Innovation of Henan Province (204200510032), the Scientific and Technological Projects of Henan Province (202102310220), the Plan of Key Scientific Research Projects of Colleges and Universities in Henan Province (20A620001), the Fundamental Research Funds for the Universities of Henan Province (NSFRF210301), and the Doctoral Fund of Henan Polytechnic University(B2019-55).
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Wen, Z., Wang, Q., Ren, J. et al. Dynamic Gas Diffusion Model of Capillary Pores in a Coal Particle Based on Pore Fractal Characteristics. Transp Porous Med 140, 581–601 (2021). https://doi.org/10.1007/s11242-021-01703-1
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DOI: https://doi.org/10.1007/s11242-021-01703-1