@article{Liu2025, 
author = {Zhongqun Liu and Jun Niu and Yabing Guo and Ying Jia and Maolei Cui},
title = {Mechanisms of CO2 enhanced gas recovery in tight-sand gas reservoirs},
year = {2025},
journal = {Energy Geoscience},
volume = {6},
number = {2},
pages = {100393},
keywords = {Tight sand gas, Diffusion, Competitive adsorption, Water lock relief, Long core displacement, Transition zone},
url = {https://www.sciopen.com/article/10.1016/j.engeos.2025.100393},
doi = {10.1016/j.engeos.2025.100393},
abstract = {Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO2 injection for enhanced recovery from tight-sand gas reservoirs. The results reveal that the diffusion coefficients of CO2 in tight reservoirs range from 10−8 m2/s to 10−9 m2/s, correlating negatively with pore pressure and positively with pore radius. In these reservoirs, CO2 manifests a significantly higher adsorption capability compared to CH4, suggesting a competitive adsorption advantage. Further, the amount of adsorbed gas correlates negatively with core permeability and positively with pore pressure. In the late-stage depletion-drive development of tight-sand gas reservoirs, CO2 injection alleviates water locking and enhances gas-water flow, facilitating the recovery of trapped gas. The long-core CO2 flooding experiment results in a 14.11 % increase in gas recovery efficiency. The effectiveness of CO2-enhanced gas recovery (EGR) is primarily related to reservoir properties. Higher average permeability correlates with more effective CO2-EGR. Although the rate and mode of injection have limited impacts on ultimate recovery efficiency, they influence CO2 breakthrough time. Specifically, a higher injection rate leads to earlier breakthrough, and the breakthrough under pulsed CO2 injection occurs later than that under continuous injection.}
}