Co-Optimization of CO2 Storage and Oil Recovery Using Alcohol-Treated CO2 Injection

CO₂ sequestration into oil reservoir is an attractive method because of enhanced oil recovery associated with it. Combining both sequestration and oil recovery in a project add more economic value. This paper investigates effect of alcohol-treated CO₂ on co-optimization of CO₂ storage and oil recovery under immiscible and near miscible conditions.

Injection experiments were performed on a Bentheimer sandstone for two sets of fluid pairs (1) CO₂ and oil, and (2) alcohol-treated CO₂ and oil. A mixture of 35% Hexane and 65% Decane was used as oil. Alcohol-treated COâ‚‚ prepared by mixing of 4% Ethanol in scCOâ‚‚ at the experimental pressure and temperature. All experiments were performed at a constant temperature of 70 ^oC and two different pressures (1300 and 1700 psi). Literature studies show that 1300 psi represents immiscible condition and 1700 psi represents near-miscible condition for the selected oil and COâ‚‚. Oil recovery, differential pressure, and compositions are recorded during injection experiments. A co-optimization function for CO₂ storage and incremental oil production is calculated by use of measured data for each experiment.

Experimental observations reveal that CO₂ storage efficiency and ultimate oil recovery is increased 10-12% and 12-15% respectively with the addition of 4% ethanol in CO₂. However, results suggest that degree of improvement in CO₂ storage and oil recovery with alcohol-treated CO₂ is more dominant during immiscible condition. Although it also shows improvement at near miscible condition, its efficiency is greatly reduced.