CO2 solubility characteristics of crude oils related to carbon capture and utilization (CCU)

Carbon Capture and Utilization (CCU) has been focused in the world to reduce not only CO2 emissions but also economical cost especially in fossil fuel energy sectors. The Laboratory of Mineral Resources Production and Safety Engineering (REPS), Kyushu University, has investigated physical properties and operation systems of the CCU, especially Enhanced Oil Recovery (EOR) and Enhanced Coal Bed Methane Recovery (ECBMR). In this review, enhanced cold oil recovery has been introduced as one of CCU applications using immiscible CO2 gas. The swelling factors of heavy and intermediate crude oils with CO2 gas dissolution were measured in a cell which pressure was less than 10MPa at expected oil reservoir temperature of 50°C. The swelling factor increased with increasing CO2 pressure. In CO2 supercritical phase, gas diffusion coefficients in oil was almost twice as high as those in gas phase. From observation of oil drainage tests using sandstone cores, gas dissolution in the oil does not make a clear effect on oil mobility; however foamy oil, included CO2 micro bubbles generated by depressurization, induced oil drainage from the oil saturated core.