Experimental Investigation of the Impact of Low Salinity Water and Hydrochloric Acid Solutions as Halite Precipitation Reduction Agents for Enhancing CO₂ Injectivity in Deep Saline Aquifers

Reducing CO₂ emissions from the atmosphere is one of the most important contributors in the fight against climate change. Salt precipitation, a critical challenge in CO₂ storage, adversely affects CO₂ injectivity by reducing formation permeability and porosity, consequently diminishing CO₂ storage efficiency. This research seeks to experimentally evaluate the effectiveness of Low Salinity Water (LSW) and Hydrochloric Acid (HCl) in mitigating salt precipitation during the injection of CO₂ into saline reservoirs to enhance injectivity. In a two-phase experimental approach, this study first simulates salt precipitation scenarios with varying brine salinities (70g/L and 170g/L) to mimic formation damage during continuous CO₂ injection. The second phase critically evaluates the impact and effectiveness of LSW and HCl as treatment fluids, as compared to freshwater. The core flooding experiments were conducted at 60 °C and 1600 psi. The initial and final permeability and porosity of the core samples were measured to ascertain the extent of improvement or impairment pre-and post-flooding using brine. The findings reveal a reduction in both porosity (11% - 30%) and permeability (28% to 75%) due to salt precipitation. LSW treatment proved to be the least effective, likely due to clay swelling. Conversely, HCl treatment exhibited high dissolution potential, achieving a 67% improvement compared to initial permeability for formations with low initial brine concentrations. Interestingly, higher brine salinity during HCl treatment resulted in an increased concentration of free ions, facilitating a rapid reaction between Cl- ions and Cu²⁺ and Fe³⁺ ions of the resulting solution. These reactions led to the formation of FeCl₃ and CuCl₂ salts causing a green coloration in the effluent. This observation suggests the possibility of tertiary reactions that could lead to other in-situ geochemical reactions and mineral precipitation.