Experimental Comparison of Nitrogen and Carbon Dioxide Oil Displacement in Carbonate Cores

Abstract

The feasibility of nitrogen and carbon dioxide flooding is being investigated experimentally as possible enhanced oil recovery processes in Iranian carbonate oil fields. Laboratory tests were conducted on a tight permeability sample of an Iranian oil field. Three flooding tests were conducted at back pressures of 1,000, 2,000, and 2,500 psi for both nitrogen and carbon dioxide separately. All tests were conducted at constant temperature of 28°C. Experimental results indicate that immiscible carbon dioxide can mobilize more oil than immiscible nitrogen due to the ability of carbon dioxide to dissolve in oil. The key factor in higher recoveries of carbon dioxide injection compared to nitrogen is the ability of carbon dioxide to extract oil components. Extraction dominates after carbon dioxide breakthrough. Although the only mechanism of oil displacement in nitrogen flooding tests was the displacement energy applied by injection pressure, the oil recoveries in nitrogen flooding are considerable, especially at higher pressures.