Potential Benefits of Fluid Optimization for Combined Smart-Water and Polymer Flooding: Impact on Remaining Oil Saturation

Abstract

Design of Smart-Water can be economically attractive owing the presence of excessive water resources (seawater). This paper aims to design Smart-Water in order to analyze its impact on remaining oil saturation reduction and hence improved oil recovery. Moreover, this study evaluates and define the synergies and benefits between high salt smart water and polymer flooding. The paper combines an extensive rheological characterization and core-flooding experiments; performing fluid optimization (change in brine composition and polymer concentration). Synthetic seawater (SSW) is used as the base brine. Optimization is perform by adding/removing specific chemical components in the SSW. Overall, five brines are utilized: 1) SSW, 2) 2*SSW, 3) SSW with double sulphates 3) SSW with quadruple sulphates and 5) SSW without NaCl. Brine 1 and 2 are used as the formation brines, whereas brine 3 to 5 are used as the injection brines to analyze impact of SO4-2 and Na+1 on remaining oil saturation reduction. Secondary and tertiary-mode experiments are performed to evaluate the feasibility of applying Smart-Water injection and its synergies with polymer flood. Smart water with spiked sulphates changed the interfacial tension compare to synthetic seawater. Henceforth smart water injection has contributed to extra oil recovery, resulting on a reduction of the remaining oil saturation due to the improved interfacial rheology and slightly higher IFT. Optimized Smart Water with spiked amount of sulphate has produced the highest oil recovery in secondary mode compared to other brines (in case of both formation brines). Furthermore, higher concentration of the divalent cations in formation brine and spiked amount of Na+1 in injected brine has resulted the significant decrease in remaining oil saturation (2*SSW as formation brine). Combination of smart water and polymer flood has shown significant reduction in remaining oil saturation. Polymer injection after smart water with spiked sulphates has contributed to significant extra oil recovery compare to the other brines owing to the combined effect of improved interfacial rheology and enhanced polymer viscoelasticity.