Mathematical model of coal seam methane displacement by injecting CO2/nitrogen

Authors

Gongda Wang, China Coal Research Institute, University of Wollongong, China University of Mining and TechnologyFollow
Ting X. Ren, University of WollongongFollow
Qingxin Qi, Central Coal Mining Research Institute
Jian Zhang, University of WollongongFollow
Lang Zhang, China Coal Research Institute

RIS ID

111367

Publication Details

Wang, G., Ren, T., Qi, Q., Zhang, J. & Zhang, L. (2016). Mathematical model of coal seam methane displacement by injecting CO2/nitrogen. Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering, 35 3930-3936.

Abstract

In order to understand the physical mechanism of coal seam methane replacement by injecting CO₂/N₂, this paper analyses the flow mechanisms of methane and injected gas during replacement and the corresponding controlling factors. Based on Langmuir model, Langmuir-like sorption swelling model, P&M permeability model and variable Klinkenberg coefficient model, the sorption model, sorption swelling model of mixed gas were proposed, and the absolute and apparent permeability models of gas injection process were improved as well. Based on above equations, a coupling mathematical model of coal seam methane replacement by injecting CO₂/N₂ was proposed by using mass conversation law. The proposed model reflects the adsorption-desorption, diffusion, Darcy flow and the additional flow from Klinkenberg phenomenon, and it can be used to calculate the gas content and pressure change, the injected and produced gas volume and the gas composition of the produced gas. This study provides theoretical foundation for the design of coal seam methane replacement by injecting CO₂/N₂.