Review on Oil Displacement Technologies of Enhanced Oil Recovery: State-of-the-Art and Outlook

Despite rapid advances in renewable energy extraction and utilization, global oil demand continues to rise. Oil displacement technologies are widely studied and applied because they can extract more oil in depleted reservoirs or recover unconventional ones. This study introduces research methods and mechanisms of four oil displacement technologies, i.e., water flooding, chemical flooding, gas flooding, and steam flooding. Although oil displacement technologies are helping to meet the growing demand for oil and energy, there are still some challenges for industrial applications. Some agents adopted in the oil displacement have shortcomings in the corrosion of mining equipment and damage to the reservoir structure. Therefore, solutions to the problem are crucial and are investigated widely in the literature using experiments and simulations. For experimental research, a diffusion framework for studying mass transfer in the oil displacement process and an experimental system for simulating oil displacement in offshore reservoirs should be built, which will facilitate the widespread industrial application of oil displacement technology. Therefore, it is necessary to improve the accuracy and expand the application range of the experimental system. As for numerical simulation, reaction kinetics research is essential for selecting displacement agent materials and preventing harmful gas leakage for industrial applications. However, the dynamics of foam flooding and CO 2 flooding are not thoroughly studied. Moreover, it is an acceptable research topic that reducing the uncertainty of discrete regions is an effective method to improve the accuracy of numerical simulation results. For the broader application of oil displacement technology to industry, several mechanisms regarding the research field could be studied more thoroughly and comprehensively in the future, i.e., (1) the influence mechanisms of some impurities and complex reservoir physical properties, (2) the method of combining various oil displacement technologies, (3) the T-H-M-C multifield coupling oil displacement mechanism at micro/nanoscale, (4) the cement failure mechanism caused by CO 2 and H 2 S, and (5) the tube brittle fracture mechanism caused by stress corrosion. For the sustainable development and efficient utilization of oil displacement, this review summarizes the extensive information about four oil displacement technologies, thus encouraging and providing research topics for further development and applications.