| Sumari: | <p>Experimental evidence shows that injecting low salinity water into an oil reservoir can lead to an increase in the amount of oil recovered. However, due to the complexity of the chemical interactions involved in this pro- cess, there has been much debate over the dominant mechanism causing this effect. Numerous mechanisms have been proposed, and, in recent years, one which has gained notable support is the multicomponent ionic exchange (MIE) mechanism.</p>
<p>The aim of this thesis is to understand how the microscale reactions de- scribed by the MIE mechanism affect the oil recovery on the macroscopic scale. We first consider a simple two-dimensional model for the motion of an oil slug through a clay pore throat in order to determine the effect of the ion-exchange reactions on the fluid dynamics at the pore scale. We further this investigation by studying two-phase flow through a three-dimensional channel with varying elliptic cross section in the limit in which the water phase is restricted to a thin film between the oil and the surface of the throat. We then investigate the effect of salinity on the permeability of a periodic porous structure for the case in which the water phase is confined to a thin film coating the solid surface, and derive a method for estimating the permeability using a network model. We develop this approach fur- ther by presenting a network model for two-phase flow through a porous structure. Finally, we use a discrete form of the method of multiple scales to homogenise our network model and derive a set of continuum equa- tions for the saturation and ion concentrations which are applicable on the macroscopic scale.</p>
|
|---|