Based on the currently discussed ability of HPAM-polymer to increase displacement efficiency due to viscoelastic properties, a comprehensive evaluation of the possible impact on the design of polymer-surfactant mixtures is presented in this investigation. This assessment includes a comprehensive analysis of laboratory experiments.
Experimental data was obtained from different sources and furthermore crosschecked, such as: rheological characterization, flooding through microfluidics devices, and core flooding experiments. First, solutions were characterized by the analysis of different rheological techniques. Second, flooding experiments were performed in a microfluidic device which has a hyperbolical contraction-expansion geometry, capable to provide apparent extensional viscosity. Third, single phase core flooding experiment was conducted using Bentheimer core plugs to evaluate the flow behavior of polymer and surfactant in porous media. Finally, flow paths of polymer-surfactant mixtures were described using streamline visualization techniques. The latter was performed injecting the solutions at different flow rates in a Glass-Silicon-Glass (GSG) micromodel generated from a micro CT scan images of a real porous media.
Polymer-surfactant mixtures depicted a pseudoplastic behavior with an increasing in polymer's apparent viscosity due to the presence of a surfactant. Polymer extensional viscosity has been slightly improved due to the addition of Polyethylene oxide (PEO) at 0.5wt% and 1.5wt% using a solvent of 4.0 g/l TDS. Increasing in the measured extensional pressure drops suggested that the viscoelastic properties are improved by using polymer-surfactant combination at apparent rates below 720s-1. Shear rate coefficients resulted in an acceptable match between the rheometer and the core flooding measurements. At a critical value of adjusted shear rates (40-50 S-1), viscosity of three solutions was almost the same value of 30 mPa.S (Critical apparent viscosity). After this critical value, HPAM with no PEO and with 0.5wt% PEO showed shear thickening behavior, while with 1.5wt% PEO showed shear thinning behavior till shear rate value of 95 S-1, after this rate, it was dominated by shear thickening behavior. Moreover, different flow regimes were observed through the streamline visualization in GSG micromodels; a zone mainly considered by laminar flow in case of HPAM with 0.5wt% PEO, remarkable vortex was observed in an open pore geometry and crossing streamlines especially in the wall areas in case of HPAM with no PEO.
This evaluation leads to understanding the viscoelastic behavior in porous media when polymer and surfactant flooding are applied in combination and provide a proper understanding to complement the few literature resources available about this topic.