Elastic Instabilities in Polymer-Solution Flow Through Porous Media

Crude oil has been an important source of energy for several decades now. Upon discovery of a crude oil reservoir until its abandonment, typically the oil recovery process can be classified in three stages. The primary and the secondary stage involve utilizing and maintaining reservoir pressure to recover oil respectively. The tertiary, or the Enhanced Oil Recovery (EOR) stage relates to employing various chemical or thermal methods to recover oil. Polymer flooding is the most promising enhanced oil recovery method that has shown potential to increase the oil recovery. Considering all the proven oil reserves from which mankind has recovered oil until now and average the oil recovery, it is less than 40%. EOR technologies have the potential to tap into the ∼ 60% crude oil that is still present in the oil reservoirs. One of the biggest technical challenges in perfecting a polymer EOR process is predicting the polymer injectivity. The viscoelastic behaviour of polymer solutions coupled with the complex pore-scale flow geometry of geological porous media gives rise to non-linear resistance to flow. Consequently, during injection of polymer solutions in an oil reservoir, the pressure-drop can increase dramatically beyond certain flow rates. This behaviour is known as apparent shear-thickening. In this thesis, we focus on understanding the apparent shear-thickening behaviour of polymer solutions as they flow through porous media. We identify the mechanism causing the non-linear resistance to flow of polymer solutions through porous media. Our experiments reveal the mechanisms at the pore-scale and also at the molecular-scale.\pa