Pore-scale simulation study on particle migration and retention in porous media during CO2 storage: effect of particle size distribution

CO₂ storage is one of the key technologies for carbon reduction. However, the storage process is often accompanied by particle migration and formation clogging, which is significantly influenced by the distribution type of particle size. Therefore, the paper studied the effect of size distribution type on particle migration and retention characteristics by coupling Computational Fluid Dynamics and Discrete Element Method. The pore-scale simulation results indicate that an increase in the mean particle radius and a decrease in the CO₂ flow velocity lead to a reduced migration capacity, higher retention rates, and closer retention positions to the inlet. Within a certain range, increasing standard deviation of particle size distribution results in higher retention rates, closer retention position, and a more concentrated retention distribution. Among different probability distributions of particle sizes, those following a chi-square distribution exhibit the highest retention rate (40.7%), followed by the exponential distribution (37.4%) and the uniform distribution (35.0%). The truncated Gaussian particles retain farther from the inlet but more concentrated, while uniform distribution has the farthest and most dispersed retention. These studies indicate that various particles with different sizes can cause a superimposed and compounded clogging performance. This combined clogging mechanism leads to a more pronounced narrowing of the pore throats than the blockage induced by large particles alone or the bridging effect caused by small particles. The findings reveal that heterogeneous particle size distributions induce more complex effects on migration and retention during CO₂ injection than single-sized particles.