Assessment of Advanced Remediation Techniques for Enhanced CO₂ Injectivity: Laboratory Investigations and Implications for Improved CO₂ Flow in Saline Aquifers

Abstract

Reducing carbon dioxide (CO 2 ) emissions from the atmosphere is a critical imperative in the ongoing fight against climate change. However, salt precipitation, a critical challenge during geological CO 2 storage, adversely affects CO 2 injectivity by reducing formation permeability and porosity, thus diminishing CO 2 storage efficiency. Although salt precipitation is a formidable challenge in geological CO 2 storage, its mitigation has not received the attention needed. The main hypothesis of this study is to experimentally verify the claim that acetic acid and HCl can improve the CO 2 injectivity in salt-induced formation damage. This study employs a two-phase experimental approach to investigate the impact of salt precipitation and subsequent remediation on the CO 2 injectivity. In Phase 1, two salt precipitation scenarios with different brine salinities of 7 and 17 wt % were used to simulate formation damage during supercritical CO 2 injection. Phase 2 focuses on evaluating the effectiveness of various treatment fluids (freshwater, low-salinity water, hydrochloric acid, and acetic acid) in restoring permeability after the formation damage. 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. Our experimental results revealed a significant decrease in permeability (28−75%) and porosity (11−34%) due to salt precipitation. Subsequent remediation techniques yielded post-CO 2 injection permeability increases ranging from 55 to 275%. However, freshwater and low-salinity water proved to be ineffective in restoring core permeability to pre-CO 2 injection levels. Conversely, acetic acid proved successful in restoring core permeability for both tested samples, while hydrochloric acid restored permeability in one of the two samples. The efficacy of acids is linked to their reactive nature, enabling dissolution and opening up pore throat. This dissolution phenomenon reduces capillary effects and facilitates fluid flow, thereby enhancing the CO 2 injectivity. Further analyses revealed salinity-dependent effectiveness of the acids, with acetic acid performing better under higher brine salinity conditions and hydrochloric acid performing better under lower salinities.