Continuous CO2 Injection for Simultaneous Geological Storage and Enhanced Oil Recovery: Experimental Investigation on the Effects of Permeability Heterogeneity

This study investigated the effects of absolute permeability on the performance of continuous CO₂ injection for a CO₂-enhanced oil recovery and storage process (CO₂-EOR and Storage) in a water-invaded zone. First, the CO₂ solubility in dead-oil and brine samples and the oil swelling factor were measured using a visual high-pressure–high-temperature cell. Following this, several continuous immiscible CO₂ injection core flooding tests at a constant rate of 0.5 cm³/min and in situ reservoir conditions were conducted. The core samples were taken from a carbonate depleted oil reservoir located in southern Iran. The results revealed that more than 30% of the injected CO₂ was trapped primarily by residual-phase and solubility-trapping mechanisms. In addition, it was found that the core samples with lower absolute permeability provided higher storage efficiency. In contrast, the ones with the highest absolute permeability showed the least potential for CO₂ storage. From the EOR point of view, on average, 18% of the residual oil was produced mechanistically through swelling as well as physical displacement. Although the results showed a declining trend in the amount of oil produced with increased absolute permeability, no clear relationship could be established.