Recovery of viscous and heavy oil by CO2-saturated brine

Abstract

Fast economic growth in Oman coupled with its climatic conditions have led to an energy-intensive lifestyle that has resulted in high levels of carbon dioxide (CO2) emissions. The injection of CO2 produced by cement plants into oil reservoirs combined with carbon capture is seen as an option to reduce CO2 in the air in order to curb climate change. The potential of CO2-saturated brine to recover oil is investigated using two samples of viscous oil (13 and 21 cP) and one sample of heavy oil (1471 cP) from Oman in water flooding experiments followed by CO2-saturated brine injection at 25 °C and 3.45 MPa. CO2 solubility in oil and brine, changes of their viscosity and density, oil swelling and other parameters are investigated. Irrespective of early water breakthrough, the greatest incremental recovery of 25.6% after injection of CO2-saturated brine through oil saturated core is obtained for heavy oil, as compared to 8.2% and 15% for viscous oils. Higher recovery from heavy oil sample is explained by the greater viscosity reduction in addition to the density reduction of CO2-saturated oil that is similar for all three types of oil of about 50% on average. The greatest reduction of oil viscosity of 87% is obtained for the heavy oil and 59% on average for viscous oil samples. Thus, different mechanisms contribute more into the oil recovery: density reduction due to oil swelling for viscose oil and viscosity reduction for heavy oil. The injection of CO2-saturated brine demonstrates a great potential in addressing both issues, curbing of climate change and energy supply by enhanced recovery of viscous and heavy oil.