Title: Dynamic response characteristics of multi-gas in coal seam during gas injection process

Authors: Gaowei Yue; Yanwen Zhang; Zihao Li; Minmin Li

Addresses: School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003 Henan, China ' School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003 Henan, China ' School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003 Henan, China ' School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003 Henan, China

Abstract: A one-dimensional gas-solid two-phase model for gas injection displacement was established, and the dynamic time-varying characteristics of gas injection displacement of multi-gas with different mixed gases were numerically analysed. The research results indicate that the permeability of coal seam N₂ slowly decreases linearly with pressure, while the permeability of CO₂ sharply decreases linearly with pressure. The numerical simulation results of the multi-gas adsorption/desorption flow model for coalbed gas injection are consistent with the measured results. Injecting a mixed gas with a high proportion of CO₂ will increase the penetration time, but increase the initial recovery rate; Injecting a mixed gas with a large proportion of N₂ will result in a lower initial recovery rate, but it will break through earlier and produce a large amount of nitrogen in the extracted gas in a short period of time. [Received: December 18, 2023; Accepted: April 20, 2024]

Keywords: gas injection replacement; multi gas; recovery rate; dynamic response; time-varying characteristics.

DOI: 10.1504/IJOGCT.2025.148042

International Journal of Oil, Gas and Coal Technology, 2025 Vol.38 No.2, pp.222 - 239

Received: 12 Dec 2023
Accepted: 20 Apr 2024
Published online: 15 Aug 2025 *

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