CO2 transport and carbonate precipitation in the coupled diffusion-reaction process during CO2 storage

During geological CO2 storage and utilization, CO2 plume migration forms widespread static retention regions including the dead-end fractures and pores in the host rock, where the mass transfer is dominated by diffusion. A series of packed column experiments with natural olivine were conducted to investigate how the coupled CO2 diffusion-reaction process influences the CO2 transport and the temporal-spatial evolution of carbonate pre-cipitation in diffusion-limited zones. The carbonate precipitations were mainly magnesite, and some dolomite due to the combined effect of carbonate precipitation kinetics and the low Ca content of the solution with Mg enrichment. Compared with the pure diffusion in porous media, the geochemical gradients in the pore solution resulting from the coupled diffusion-reaction interaction promoted mass transfer and broad migration, which led to an increase in effective diffusion coefficients of CO2 by approximately-one order of magnitude. The free water layer and pressure mode could affect the distribution of carbonate precipitation and the overall sequestration capacity. In particular, the coupled CO2 diffusion-reaction interaction under pressure decay mode could accel-erate the carbonation in the deep region in the water-saturated column. This study advances the fundamental understanding on the transport and reaction of injected CO2 for mafic and ultramafic formations.

Automated summary

This study investigates the influence of the coupled CO2 diffusion-reaction process on the transport and temporal-spatial evolution of carbonate precipitation. The results show that the interaction between diffusion and reaction promotes mass transfer and migration, leading to an increase in effective diffusion coefficients of CO2. The distribution of carbonate precipitation and sequestration capacity are affected by the water layer and pressure mode.