Simulation study on surface deformation characteristics of CO2 storage in abandoned goaf

Abstract

In order to explore the characteristics of surface deformation caused by supercritical CO2 injection into abandoned goaf, the general characteristics and evolution process of surface deformation were studied by FLAC3D simulation. The effects of porosity, CO2 injection rate and storage depth on surface deformation characteristics were discussed from five aspects, such as deformation range and deformation amount. The results show that the surface deformation caused by CO2 injection into the abandoned goaf is in the form of “inverted bowl” uplift, and experiences the evolution process of incubation stage, active stage and stable stage. As the surface point is far away from the goaf, the proportion of its displacement in the incubation stage and the stable stage gradually increases. The surface deformation range decreases significantly with the increase of CO2 storage depth, and is less affected by the change of porosity and CO2 injection rate. The surface displacement gradually decreases with the increase of porosity and CO2 storage depth, and is less affected by the change of CO2 injection rate. The duration of surface deformation is positively correlated with porosity and CO2 injection rate, and negatively correlated with CO2 storage depth. The proportion of the displacement of the surface point in the incubation stage and the stable stage is positively correlated with the number of time steps required and the porosity and storage depth, and negatively correlated with the CO2 injection rate.

Keywords

• abandoned mines
• carbon dioxide storage
• goaf
• surface deformation
• numerical simulation