| الوصف: |
Enhanced oil recovery (EOR) is a method used to improve oil production. However, the performance of oil recovery by EOR deteriorates due to rock heterogeneity, reservoir conditions, and formation damage as a result of chemical adsorption to the rock surface. Recently, it has been found that under two-phase flow conditions, there is an existence of stagnant and flowing zones. The presence of the stagnant zone reduces the performance of the EOR because this zone does not contribute to the effective permeability, which is defined as the ability to transmit a particular fluid in the presence of another immiscible fluid in the porous medium, as well as to advective transport. The purpose of this thesis is to characterise the stagnant and flowing zones, and hence, quantify the amount of the stagnant zone present (measured as stagnant saturation) through pore-network modelling and x-ray imaging. Numerical results show that there is a linear relationship between total relative permeability deficit and stagnant saturation. Total relative permeability deficit is defined as one minus the sum of the relative permeability of a receding fluid and invading fluid for a given saturation value, where relative permeability is the ratio of effective permeability of a particular fluid that can be either invading fluid or receding fluid to the absolute permeability. While experimental results demonstrate that under the same saturation value but different flow rates (measured as Peclet number), a distinct solute behaviour is observed. At a low flow rate, the solute behaviour shows Fickian behaviour, while at a high flow rate, the solute behaviour indicates non-Fickian behaviour. Furthermore, stagnant saturation and transport parameters have usually been estimated through curve fitting of the experimental data to the two-phase flow transport models. In this study, the stagnant saturation and transport parameters are directly estimated using pore-network modelling approaches. To benchmark the direct estimation method with the curve fitting technique, the results show that the direct estimation method is the preferred model to explain solute transport under two-phase flow condition as compared with the time-based model of the continuous time random walk model, the phenomenological model of the mobile-immobile model, and the multirate mass transfer model. |
