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

Abstract

Abstract 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.