Predicting the viscosity of solutions used in polymer flooding applications

Enhanced oil recovery techniques offer alternative methods for extracting crude oil. For example, polymer flooding modifies the viscosity of water with polymer to speed up and improve the oil recovery of a reservoir. Stephane Jouenne and Bertrand Levache developed a modeling approach that captures the non-Newtonian behavior of these water-soluble polymer solutions.

For more than a decade, researchers have studied, mostly in simulations, the effect of polymer viscosity on oil recovery based on physicochemical conditions such as temperature, salinity, ionic composition, and polymer grade. However, no physical model has been used to test and verify the findings from these studies, and their reliability remained unknown.

Jouenne and Levache combined a plethora of experimental measurements with existing theories of polymer dynamics. They analyzed the flow curves, i.e. viscosity as a function of shear rate, of more than 400 solutions consisting of polymers/brine solutions with different concentrations. The acrylamide-based copolymers had different microstructures, monomer compositions and molecular weights, while the brines varied in terms of salinity and temperature.

The flow curves were fitted with a Carreau-type equation based on scaling laws of polymer physics to extract the intrinsic viscosity and relaxation time in the dilute regime of the polymer/solvent system.

From their modeling approach, the solution viscosity can be predicted at any shear rate, polymer concentration, temperature, and molecular weight from one single rheological measurement.

Next, the authors hope to study the link between the bulk viscosity of the solution and the apparent viscosity observed in porous media, which differs due to the confinement of the polymer chains in the pores.

Source: “Universal viscosifying behavior of acrylamide-based polymers used in enhanced oil recovery,” by S. Jouenne and B. Levache, Journal of Rheology (2020). The article can be accessed at http://doi.org/10.1122/8.0000063 .