One of the major challenges of modern society is the increasing demand for energy, and conventional resources such as oil and natural gas are crucial for meeting this challenge. Hence it is of paramount importance to enhance the recovery process of these resources with a sustainable and environment-friendly approach. An incremental oil-output from the reservoir is achieved via Enhanced Oil Recovery (EOR). This thesis focuses on one of these processes, namely wettability alteration, where turning a oil-wet reservoir-rock into a waterwet surface releases oil droplets and ensures an incremental recovery. First, we investigate the competitive wetting of aqueous salt solution and an oil (decane) on mineral surfaces, where we observe a transition from a (nearly) complete wetting of monovalent salt (NaCl, KCl) solutions on mica, to a partial wetting state when divalent salt CaCl2 at high concentration and pH is present in the aqueous solution. We theoretically investigate the intermolecular interactions in our system, especially the electrostatics, which led to the wetting transitions. Subsequently, we focus on the more subtle influence of van der Waals and hydration interactions upon wetting. A transition from (nearly) complete wetting to partial wetting is found in a mica-water-alkane system, if the cation-size is increased while keeping the valency same. In doing so, we present a hitherto unreported cationic adsorption/wettability sequence which resembles the famous Hofmeister series of protein crystallization. Finally, we investigate the effects of surface-active fatty acid in ambient oil on aqueous drops wetting mica and silica where a spontaneous increase in contact angle (autophobing) is observed in presence of divalent cations in the aqueous phase at a high pH. Thus, we demonstrate wettability alterations in relevant systems driven by ionic species and surfactants, and theoretically model the underlying physics of such phenomena.
|Award date||12 Feb 2016|
|Place of Publication||Enschede|
|Publication status||Published - 12 Feb 2016|