Characterization of Salt Precipitation Behavior in a Carbonate Formation Under Reservoir Conditions Using Low-Field Nuclear Magnetic Resonance

CO2 geological storage in saline aquifers is considered as the most promising approach to reduce carbon emissions. The injected CO2 will evaporate the brine, resulting in salt precipitation in the formation. Traditional experimental studies of salt precipitation at core-scale exhibit insufficient measurement accuracy and fail to quantitatively assess the impact of salt precipitation on the pore structure characteristics of core sample. Herein, we presented a work on the kinetics of salt precipitation during CO2 geological storage in a typical low-permeability carbonate reservoir. Special attentions were given to the influences of pressure, flow rate, temperature and salinity, etc., on salt precipitation at the core scale using Low-field NMR technology. The findings indicated that the temperature and salinity could greatly affect the salt precipitation since the maximum reduction in permeability reached 52.95%, while porosity reduction reached 28.48% at 200000 mg/L and 100 °C. The increase in flow rate (10 to 15 ml/min) might strengthen the ability of CO2 to carry brine and mitigate the capillary back flow effect, thereby reducing the salt precipitation. The significant deviation in the one-dimensional signal spectrum indicated that salt precipitation predominantly occurred at the forefront of the core. Additionally, the injection pressure showed minimal influence on salt precipitation under varying salinity levels. Salt precipitation caused greater damage to the petrophysical properties of core with low-permeability. This study offered guidelines for mitigation strategies to minimize the adverse impacts of salt precipitation.