Pore-Scale Experimental Investigation of the Supercritical CO2 Injection Rate and the Surface Wettability on Salt Precipitation.

Abstract

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into the saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation are not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at reservoir temperature and pressure. It is found that for the hydrophilic and neutral porous surface, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing CO2 injection rate can suppress the capillary reflow and prevents the permeability reduction. For the hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples under the same injection rate. Increasing CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity.