An innovative technique and laboratory protocol for CO2 storage in water disposal wells and monitoring asphaltene deposition

Injecting CO₂ into water-disposal wells is a promising strategy for geological carbon storage. However, this process can destabilize asphaltenes in residual oil blobs-primarily of the emulsified type - trapped within trapped in the porous rock, leading to precipitation that threatens storage integrity and operational safety. This study introduces a novel high-pressure laboratory apparatus and protocol designed to directly quantify asphaltene precipitation during CO₂ injection into oil-in-water emulsions, which represent water-flooded formations. The system operates at reservoir-relevant conditions (up to 11,000 psi and 210 °C) and utilizes in situ near-infrared (NIR) light transmission to monitor asphaltene precipitation in real-time. Additionally, this research investigates the behavior of the oil-in-water emulsion (EM) phase as the medium hosting CO₂ gas under different conditions. Quantitative results, expressed as the percentage reduction in NIR transmission, showed that asphaltene precipitation was minimized to 0.8% under optimal conditions (2DSW, 120 °C, 50 mol% CO₂), compared to a peak of 25.1% in the worst-case scenario (FW, 30 °C, 35 mol% CO₂). Regarding the CO₂ injection rate, less asphaltene precipitation occurred at higher injection rates. In this case, crude oil vaporized in the EM phase at high CO₂ injection rates (above 35 mol%), resulting in fewer crude oil droplets available to interact with CO₂. Notably, EMs prepared with twice-diluted seawater (2DSW) exhibited the least asphaltene precipitation, a finding strongly correlated with lower oil/water interfacial tension. Overall, the developed protocol provides a critical tool for screening and de-risking CO₂ storage sites in water-disposal zones by enabling accurate prediction of asphaltene-related damage.