ABSTRACT: The application of smart water−polymer hybrid
flooding in sandstone reservoirs has gained significant attention in
recent years. This study provides a comprehensive review of the
smart water−polymer flooding concept, including the underlying
mechanisms, necessary conditions, and specific applications in
heavy oil sandstone reservoirs. Screening criteria and required
conditions for each method are investigated thoroughly to ensure
the possibility of their synergy. The study also addresses smart
water deficiency as a single Enhanced Oil Recovery (EOR) process
for heavy oil heterogeneous sandstone reservoirs. The effectiveness
of smart water−polymer hybrid flooding in terms of enhancing oil
recovery mechanisms, various injection scenarios, economic
profitability, and associated risks such as injectivity decline and
viscosity loss is thoroughly examined and compared in different experimental and simulation studies. Based on the literature, it is
concluded that wettability alteration and mobility control are the main controlling mechanisms. The synergistic effect of these
mechanisms can lead to an increase in oil recovery equal to or higher than the summation of each method separately, with more
effective results for heavy oil reservoirs. Notably, among the various injection scenarios explored, smart water injection followed by a
tertiary smart water−polymer flood demonstrated the highest ultimate oil recovery. Despite numerous experimental studies on this
subject, a series of controversial results have been observed concerning issues such as injectivity, polymer retention, and cation
exchange between the polymer and aqueous phase. This indicates the necessity for more detailed investigations on this hybrid EOR
method in the future. Simulation and optimization studies, particularly by applying proxy models such as artificial-intelligence-based
methods, seem to have a high potential for further field study in this topic.