Preventive Strategy for Salt Precipitation Control During Supercritical CO2 Injection into Saline Aquifers Using Nonionic Surfactants

Salt precipitation during supercritical carbon dioxide (scCO2) injection into saline aquifers remains a major challenge for carbon capture and storage (CCS) operations, severely impairing near-wellbore injectivity and threatening long-term storage performance. Most existing mitigation strategies rely on reactive postdamage treatments, such as freshwater or chemical remediation, which are often temporary and may introduce secondary formation damage. This study evaluates nonionic surfactant preinjection as a preventive strategy to suppress salt precipitation during scCO2 injection. Core-flooding experiments were conducted on Berea sandstone cores saturated with NaCl brine of 70000 and 200000 ppm under supercritical conditions (55 °C, 1,600 psi). Two nonionic surfactants, Tween 80 and Triton X-100, were injected at 1500 ppm before scCO2 flooding and compared to untreated baseline cases. Surface tension and turbidity measurements indicated surfactant stability and salinity tolerance before core-flooding. Untreated cores showed pronounced differential pressure (dP) buildup and severe permeability impairment due to salt precipitation, with permeability retention decreasing approximately to 49% and 32% at 70000 and 200000 ppm, respectively. Conversely, surfactant-treated cores exhibited reduced pressure buildup, delayed salt precipitation, and permeability retention of up to 65%. Triton X-100 outperformed Tween 80 across both salinities, producing lower stabilized dP and more consistent pH responses. Visual inspection of postflood cores further confirmed reduced salt accumulation in surfactant-treated systems. These results demonstrate that nonionic surfactant preinjection offers an effective and preventive approach for mitigating salt precipitation and maintaining injectivity during CO2 storage in saline aquifers.