Mitigating Salt Precipitation in CO2 Storage Through Humidified Injection: An Integrated Experimental-Numerical Study

Abstract

Abstract Halite precipitation caused by brine drying out can seriously damage near-well permeability and reduce injectivity during CO2 storage in deep subsurface brine formations. This research employs the integration of high-pressure decay tests with the compositional reactive transport modeling to examine the potential of water-enriched CO2 injection in order to mitigate the impact of salt precipitation and improve CO2 performance. CO2 diffusion coefficients measured experimentally in brines of different salinities were incorporated into a three-dimensional heterogeneous CMG-GEM model. Injection-rate sensitivity analysis was conducted initially under the constraint of a maximum bottom-hole pressure (BHP) of 55,500 kPa, followed by systematic investigation of H2O contents of 0–20 mol% and different formation brine salinities of 10,000–100,000 ppm NaCl. Accumulation of salt, near-well permeability, BHP, injectivity index, and CO2 dissolution efficiency were quantified. An injection rate of 4,000 m3/d per well was optimized as having a safety margin of approximately 2.99 MPa with respect to the applied constraint. Adding 5 mol% of H2O could reduce halite accumulation from 78,560.02 gmol to 364.28 gmol, translating to a 99.54% reduction, while further addition of H2O provided only marginal benefit. Under this condition, 97.05–99.73% of salt could be effectively suppressed. In comparison to dry CO2 injection, water-enriched injection preserved approximately 23% higher permeability, reduced the stabilized BHP by 7.06%, and improved the injectivity index by 10.09%. Long-term dissolution efficiency increased from approximately 45.7% to 52.8%, representing a relative enhancement of 15.5%. The results prove that modest water enrichment can concurrently suppress salt-induced formation damage, reduce injection-pressure requirements, sustain injectivity, and enhance dissolution trapping, providing an operational basis for improved CO2 storage performance in saline aquifers