Carbonated water injection: Effects of silica nanoparticles and operating pressure

Carbonated water injection (CWI) is the process of injecting CO₂-saturated water into hydrocarbon reservoirs as a displacing fluid. As CO₂ is dissolved in and transported by the flood water, CO₂ is more evenly distributed within the reservoir, improving sweep efficiency, which is beneficial to watered-out oil reservoirs, where high water saturation can adversely affect the performance of conventional CO₂ injection. The effects of increasing CO₂ concentration in water using silica nanoparticles, and of pressure on the CWI process were evaluated through a number of high-pressure coreflooding experiments. The experiments were conducted in a highly water-wet core, using normal decane as the oil phase. The results revealed an increase in ultimate oil recovery as the level of CO₂ concentration in water increased. In the application of nanoparticles, an optimized concentration of nanoparticles must be used to obtain the maximum oil recovery factor. CWI showed a higher recovery factor both in the secondary and tertiary modes at higher pressures, due to the increased solubility of CO₂ in water at high pressures. These suggest that secondary CWI performs better than tertiary recovery, due to the high probability of contact between the oil and the CO₂ gas and a growing concentration of CO₂ in the water.