Associative polymer-based fluids for enhanced oil recovery using produced saline water

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In Canada, chemical flooding is currently being applied to increase recovery from a number of medium and heavy oil pools in the Lloydminster region of eastern Alberta and western Saskatchewan. According to the Government of Alberta's Innovative Energy Technologies Program, chemical-enhanced oil recovery (cEOR) could potentially add 80 million m3 of oil to Alberta and Saskatchewan's reserves in the next 20 years. While in the U.S.A. alone approximately 1 billion pounds of polymers were used for cEOR, the potential of chemical flooding in unconventional tight oil remain largely unexplored. In cEOR operations, various chemicals such as polymers, surfactants, alkali or combinations thereof are injected into wells to increase oil recovery. However, different reservoir operating conditions (e.g. pH, temperature, salinity, dissolved iron and oxygen, and presence of alkali and/or surfactant) affect polymer structure and size. Water-soluble polymers with a small amount of hydrophobic character (referred to as Associative Polymers) have huge potential for EOR efficiency even with produced or saline water. Despite selective success in laboratory research in recent years, a comprehensive and predictive knowledge to answer key questions remains elusive. This proposal focuses on understanding mechanisms during associative polymer flooding for applications in conventional and tight oil reservoirs and creating a predictive model. Saline water and smart water can have a positive effect on associative polymer injectivity and transport properties due to polymer coil expansion. Synergistic effects between associative polymer, surfactants, and ionic interactions can lead to increased EOR efficiency even for carbonate reservoirs. The mechanism due to associative polymeric flooding and the salinity effect haven't been clearly distinguished; therefore, optimal design cannot be achieved. Moreover, the conventional capillary number calculated using the shear viscosity and apparent viscosity does not explain the various residual oil recovery shown by these associative viscoelastic polymer solutions at different salinity. Also, rapid oil mobilization for viscoelastic polymers begins to occur at a capillary number lower than the critical capillary number. Therefore, there is a strong need to re-establish capillary concept by modifying the conventional definition of capillary number and developing a capillary desaturation curve for viscoelastic associative polymer--based fluids. In summary, the synergistic effects between ionic solution, hydrophobic group contents and surfactants have huge potential influences viscosity and extensional properties and/or wettability, besides other mechanisms, and thereby EOR and fracking efficiency. The proposed research program will address key technological gaps in EOR using associative polymer based fluids.