Innovative soaking-enhanced carbonated water flooding for EOR and CO2 storage

Abstract

This study introduces an innovative soaking-enhanced carbonated water flooding protocol, which significantly enhances oil recovery and CO₂ sequestration by incorporating a soaking stage. The effects of soaking-enhanced carbonated water flooding on oil recovery and CO₂ sequestration were systematically examined through sand-packed tube flooding experiments under varying CO₂ concentrations, reservoir permeabilities, and oil viscosities. The results demonstrate that the soaking stage significantly enhances the performance of carbonated water flooding, improving both oil recovery and CO₂ sequestration across all tested scenarios. This enhancement is achieved by extending the interaction time between carbonated water and reservoir fluids, allowing dissolved CO₂ to fully diffuse into the oil phase. The CO₂-enriched oil undergoes viscosity reduction and volumetric expansion, collectively enhancing oil mobility and recovery efficiency. Simultaneously, pressure equilibration during soaking redistributes CO₂ into micropores and dead-end spaces, increasing storage efficiency and minimizing gas release. These effects are evident in production dynamics, where soaking leads to rapid recovery of oil production, significant reductions in water cut, and minimized gas release. The benefits of soaking are particularly pronounced under conditions of higher CO₂ concentrations, higher reservoir permeability, and lower oil viscosity. For instance, at 0.8 mol/L CO₂, oil recovery increased from 56.35 % to 73.38 %, and CO₂ storage rose from 0.12 to 0.16 pore volumes. High-permeability reservoirs (2103 mD) achieved oil recoveries of 85.12 % and CO₂ storage of 0.18 pore volumes, while low-viscosity oils (16.1 mPa s) exhibited recoveries of 84.40 % and storage efficiencies of 0.19 pore volumes. In summary, the soaking-enhanced carbonated water flooding protocol provides a robust and scalable solution for enhancing oil recovery and CO₂ sequestration. Its broad applicability and adaptability to diverse reservoir conditions make it a transformative technology for sustainable energy production and carbon management.