Simulations and Experiments Analysis of Induced Behavior of Low-Permeability Sandstone by CO2 Injection

Abstract

Global demands for carbon emissions reductions and the shift toward a green, sustainable energy sector have highlighted the secure and steady injection of CO2 into underground layers as a key component of carbon storage initiatives. Unlike geological storage in high-permeability reservoirs, it is crucial to clarify the migration and reservoir response of CO2 in low-permeability geological reservoirs. To address this, core permeability experiments and low-rate injection experiments were designed, and the physical parameters and induced behaviors of sandstone samples were analyzed using wave velocity measurements, computed tomography (CT) scanning, and scanning electron microscopy (SEM) technology. The results show that (1) after CO2 is injected into low-permeability sandstone samples, the porosity and pore size of the rock increase significantly; (2) CO2 injection into low-permeability sandstone can induce small-scale fracture propagation, which elucidates the microscopic mechanisms behind microseismic events when CO2 is injected at a low rate; and (3) the events monitored during CO2 injection into low-permeability reservoirs directly characterize the fluid migration area. CO2 injection experiments combined with particle flow code-distinct element method (PFC-DEM) numerical simulations reveal the microscopic mechanisms of CO2 penetration and fracturing in low-permeability reservoirs with low-displacement injection. These findings provide a basis for predicting the diffusion and migration patterns of CO2 during carbon storage, as well as its fracturing behavior. The characterization of fracture distribution contributes to the detailed description and interpretation of microseismic monitoring data, helping prevent CO2 leakage due to unpredictability in engineering, thereby ensuring the effective implementation of carbon sequestration projects and supporting ecological safety monitoring and protection.