Abstract

A polymer flooding Pilot in Brazil showed positive results and distinct from other Pilots, in terms of increased oil production and reducing the water produced. These results, however, could not be attributed to viscosity correction - the fundamental principle of the process according to literature -, because the combination of adverse conditions of application, such as high salinity and hardness of the water reservoir, heterogeneity and canalization formation, as well as reduced injected polymer mass. The aim of this work was to reproduce in laboratory scale the phenomenon observed in Pilot. The laboratory flow tests were performed at constant rate in natural porous media, in the range of 100 mD and 1000 mD, and in metallic porous media 60000 mD, at HPAM concentrations of 10 ppm and 1000 ppm, salinity 38000 ppm and temperature 50 °C. The injectivity field test was conducted at concentrations of 300, 500 and 1000 ppm, followed by water injection and monitored with tracers. The residual resistence factor (RRF) as a result of the flow of the HPAM solution at very low concentration (10 mg/L) was much higher than RRF due to the flow of concentrated HPAM solution (1,000 mg/L). As unexpected, in the field, presenting significant finger, the lowest pressure occurred at the highest polymer concentration. The tracer test confirmed the significant decrease in permeability after HPAM injection. Evaluations reported show that the concentration regimes of HPAM dispersions are highly impactful in the flow in porous media, and could be related also to the polymer hydrodynamic volume. As an example, injection of a polymer dispersion of 10 ppm caused a higher factor of residual resistance than the promoted by dispersing 1000 ppm, even at high salinity and high permeability conditions. The results extend our understanding of the mechanisms governing the behavior of polymer dispersions in porous media, particularly in the process of correcting mobility in mature fields.

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