Unraveling the Dynamics of Polymer Scission in Porous Media

The flow of polymer solutions in porous media has tremendous utility for subsurface energy operations, water remediation, and packed bed reactors. The tortuous geometry of the pore space generates velocity gradients that, when sufficiently strong, cause polymers to undergo a coil-stretch transition where the polymer coils begin to extend. While this process has been studied in simplified geometries, how it manifests in more complex porous media is not well understood. It is crucial to understand what drives this process as fully extended polymers are subject to break, resulting in two lower molecular weight polymers. Continued degradation of polymer solutions ultimately reduces their efficacy. Here, we use pressure drop measurements of polymer solutions flowing through porous media to characterize the extent of scission during this process. We present a universal curve of scission that shows the generality of this process across various flow rates, pore sizes, polymer concentrations and molecular weights. Improving our understanding of polymer scission will provide fundamental insights in complex fluid dynamics and will provide quantitative guidelines for the use of polymer solutions in the aforementioned applications.