Polymer Stability Following Successive Mechanical Degradation Events

摘要

A key challenge in polymer flood forecasting is the prediction of polymer stability far from the injector Degradation may result from various mechanical degradation events in surface facilities and at the wellbore interface, as well as possible oxidative degradation due to the presence of oxygen and reduced transition metals All these steps must be closely examined in order to minimize degradation and ensure propagation of a viscous polymer solution. In this paper, polymer solutions are pushed towards unacceptable degradation rates for EOR application in order to better understand the underlying physics. Multi-step degradation events are induced in various geometries, such as capillaries, blenders, constrictions, and porous media. Whatever the geometry, degradation approaches an asymptotic value as the number of degrading events increases. Degradational kinetics curves of the different geometries can be superimposed by normalizing the number of degrading events By comparing various geometries, we demonstrate that degradation in porous media reaches a stable value after passing through approximately 6 mm of rock. Moreover, previous degradation history strongly affects subsequent degradation when multiple events occur, suggesting that both molecular weight distribution and degrading geometry are key factors in degradability. Thus, multiple measurements are required in order to determine the degradability of a polymer solution. In absence of simple means of characterization of the molecular weight distribution such as size exclusion chromatography, a protocol is proposed so as to estimate the mechanical degradation following multiple degrading events based upon a two-step laboratory experiment.