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The decline of mature oil fields has intensified the development of enhanced oil recovery (EOR) methods capable of improving sweep efficiency under harsh reservoir conditions. Polymer flooding is widely applied to control the mobility ratio between injected water and oil; however, conventional polyacrylamide-based polymers often exhibit limited performance in high-temperature and high-salinity reservoirs due to chemical and mechanical degradation.
This work presents a comparative experimental study of the flow behavior of thermoresponsive associative polymers (TRP) and conventional partially hydrolyzed polyacrylamide (FLOPAAM class) under conditions representative of Brazilian pre-salt reservoirs (80 °C and 104,000ppm TDS). The analysis combines bulk rheological characterization with single-phase coreflooding experiments conducted in Bentheimer sandstone cores, allowing direct assessment of polymer transport and flow resistance in porous media.
Polymer solutions were prepared under oxygen-free conditions to minimize oxidative degradation. Coreflooding tests were performed at different flow rates, and the resulting differential pressure responses were used to calculate, in steady state, the resistance factor (RF) and residual resistance factor (RRF). Rheological data were correlated with porous media responses to elucidate the relationship between solution behavior and in situ apparent viscosity.
The FLOPAAM solutions exhibited typical shear-thinning behavior, with average RF and RRF consistent with conventional polymer flooding performance under high-salinity conditions observed in the literature. The flow behavior was well described by the Power Law model combined with the Cannella correlation. In contrast, the thermoresponsive associative polymer (TRPs) showed a markedly different response, with significantly higher RF and RRF, indicating apparent viscosity 100 times higher than bulk values obtained from rotational rheological measurements. A complete extensional rheology characterization is being conducted in order to properly identify the mechanisms responsible for the great difference between shear and core-flooding apparent viscosity values.
Core-flooding experiments already demonstrated the superior ability of TRP systems to modify flow resistance in porous media under extreme reservoir conditions, highlighting their potential as advanced mobility-control agents for EOR applications. The pursuit of detailed descriptions of mechanisms that dominate this flow constitute a first step toward the development of predictive models for TRP transport in porous media.
Ongoing work includes two-phase coreflooding experiments to evaluate oil recovery factors and establish correlations between polymer rheology, relative permeability alteration, and displacement efficiency.
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| Country | Brazil |
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