Progress and Outlook of Supercritical CO2–Heavy Oil Viscosity Reduction Technology: A Minireview

Under the guidance of the carbon peaking and carbon neutrality strategies, the recovery, emission reduction, and effective utilization of industrial CO2 are particularly important. Supercritical CO2 viscosity reduction technology effectively improves the flowability and reduces the energy consumption of heavy oil pipeline transportation. This work reviews the experimental research on supercritical CO2 viscosity reductions of heavy oil, summarizes the viscosity reduction mechanisms and main influencing factors, describes the research achievements regarding theoretical parameters such as the solubility and viscosity of supercritical CO2 and the density and viscosity of live oil, introduces engineering applications of supercritical CO2 in the oil and gas field, analyses the problems involved in corrosion, stability, and solids deposition of crude oil containing dissolved CO2, and presents the current challenges and perspectives. The main future research directions of this technology involve the mechanism of supercritical CO2 viscosity reduction, ensuring the stability of supercritical CO2 and crude oil mixtures during pipeline transportation, designing and establishing oilfield surface engineering facilities for supercritical CO2 viscosity reduction technology, and improving the protection strategies for CO2 corrosion. This work can provide a reference for the application of supercritical CO2 in heavy oil development and pipeline transportation.