DOI: https://doi.org/10.55373/mjchem.v28i2.291

Keywords: Saline aquifers, salt precipitation, CO₂ injectivity, nonionic surfactants, chemical pre-treatment

Abstract

Salt precipitation in saline aquifers adversely affects carbon dioxide (CO₂) injectivity, posing significant operational challenges for geological carbon storage projects. This study investigates the potential of Tween-80 as a chemical pre-treatment to mitigate salt precipitation during supercritical CO₂ (scCO₂) injection into sandstone saturated with 200000 parts per million (ppm) sodium chloride brine. Before the core flooding experiments, the turbidity and critical micelle concentration (CMC) of Tween-80 in the high-salinity brine were measured as 0.56 nephelometric turbidity unit (NTU) and 12.6 ppm, respectively. Core flood tests on a Berea sandstone core with an initial brine permeability of 311 millidarcy (mD), porosity 23.57% were run at 1650 psi and 50°C, after Tween-80 was pre-injected at 0.5 ml/min. The pre-injection of surfactant produced a clear short-term improvement where permeability rose to 393 mD, indicating improved flow capacity during treatment. However, the final brine permeability reduced to 136 mD after CO₂ injection, and salt precipitation was observed, indicating that the single high-concentration pre-flush was insufficient to prevent CO₂-driven salt precipitation under the experimental sequence and condition. These findings demonstrate that Tween-80 can transiently enhance injectivity, but effective mitigation of salt plugging in extreme-salinity conditions will likely require optimized dosing strategies or alternative treatment approaches.