Salt precipitation-induced formation damage near the wellbore: Implications for underground hydrogen storage

Underground hydrogen storage in saline aquifers presents several technical challenges, particularly evaporation-induced salt precipitation near the wellbore leads to injectivity loss and poses serious constraints on the long-term operability of storage sites. This study utilizes field-scale models which integrate flow dynamics with gas-liquid-solid phase equilibria and geochemical simulations to enable assessment of halite deposition rates, timing, and the resulting impact on reservoir integrity. Results reveal that severe salt deposition occurs only under specific conditions, and its effects become significant over extended injection periods. In the cases examined, salt deposition increased bottomhole injection pressures by up to 1300 psi and reduced porosity by 0.005 in a reservoir with an initial porosity of 0.15 and permeability of 100 mD. Sensitivity analyses further show that increasing injection rates from 10,000 ft³ /Day to 150,000 ft³ /Day and durations can expand the damage radius from 1 ft to 4.5 ft. Moreover, increasing the reservoir permeability from 10 mD to 150 mD results in a higher bottomhole injection rate and leads to a 2-ft expansion in the radius of salt precipitation. The results indicate that the amount of salt precipitated in a reservoir with a formation water of 7.17 Molal salinity is significantly higher than that in a reservoir containing fresh water, but the damage radius does not change significantly as salinity increases. The purity of the injected hydrogen gas was found to have a significant impact on the radius of the damage zone. When the injected gas comprised a mixture of 25% hydrogen and 75% methane, the radius of damage extended to approximately 4.5 ft, in contrast to only 2 ft observed with pure hydrogen injection. The initial water saturation of the formation can also impact the damage radius such that decreasing water saturation from 0.9 to 0.3 leads to reduction of the dry-out radius by approximately 2 ft. Overall, it is found that salt precipitation requires a certain combination of the parameters. The most influential factors affecting the extent of salt precipitation and the associated formation damage are formation water salinity, injection rate, duration of hydrogen gas injection, formation porosity and water saturation. Variation of initial salinity, porosity, and permeability affect the compactness of salt deposition and injectivity, without significantly changing the dry-out zone radius.