Enhanced heavy and extra heavy oil recovery: Current status and new trends

Due to the increased demand for energy resources these days, especially due to the Russian-Ukrainian war, the focus of the major countries is turning strongly towards improving oil production, especially heavy and extra heavy oil, which represents 40% of the world oil reserve. Steam-based and thermal (EOR) procedures are promising techniques for recovering heavy oil reservoirs, but they suffer from a sequence of problems and complications that arise after long-term application. These complications comprise steam breakthrough, steam overlap, and steam/rock interactions. This research presents the currently applied techniques to maximize the productivity of heavy oil, such as steam injection, cyclic steam stimulation, in-situ combustion, and steam-assisted gravity drainage. Thermal technologies face numerous obstacles, as they are energy and water-intensive processes that are not environmentally friendly. The research also presents future trends in energy-saving and environmentally friendly techniques that enhance heavy oil recovery through vapor extraction (VAPEX) steam-solvent hybrid techniques, electromagnetic energy, sonication, and nanotechnology. The findings of this review reported that all the presented techniques focus on how to reduce the oil viscosity and in-situ upgrade the crude oil properties. In turn, these enhance both the productivity rate and oil recovery and minimize the production cost. This article can be considered a comprehensive review of thermal recovery methods in heavy and extra-heavy oil, in addition to screening criteria used for each method.