Study of the Intervening Thin Liquid Film between Deformable Oil Drop/Bubble and a Solid Surface in Oil Production
Creators: Tianzi Bai
Publisher: name: University of Alberta Library
Year: 2022

<p>Interactions involving deformable bubbles/oil droplets play a critical role in many industrial applications. Understanding the dynamic thin film drainage process and interaction forces involving deformable bubbles/oil droplets and solid surfaces in the oil sands extraction process is of great importance fundamentally and practically. However, due to the complexity of bitumen, dynamic interactions involving bitumen are not fully understood. In this study, the bubble probe atomic force apparatus (AFM) technique and the dynamic force apparatus (DFA) were applied to study the interaction forces and film drainage process respectively, including bubble-bitumen interaction and bitumen-solid interaction. A theoretical model was developed to describe the interaction forces and also the film drainage process under different water chemistries. In addition, the mechanism of chemicals modifying the bitumen/water interfaces was also investigated.<br><br>
The effect of a novel secondary processing aid, sodium citrate (Na3Cit), on bitumen aeration was investigated. The bubble probe AFM technique was applied for direct measurement of the interaction between an air bubble and a bitumen coated silica wafer. It has been found that the pure Na3Cit solution could prevent bubble-bitumen attachment due to the strongly more negatively charged bitumen/water and air/water interfaces. However, in the presence of Ca2+, the addition of Na3Cit would not prevent bubble-bitumen attachment when the solution ionic strength is high enough. The Stokes-Reynolds-Young-Laplace model was successfully implemented, predicting the interaction forces under all conditions. It proved that the competition between the electrostatic double layer (EDL) repulsion and the hydrophobic (HB) attraction was the main reason that controlled the bubble-bitumen attachment. A stability map was established to reveal the attachment between bubble and bitumen in different water chemistries to guide the industrial applications. <br>
An investigation was conducted to reveal the mechanism of how Na3Cit modifies the bitumen/water interface and affects the zeta potential. The results showed that the chemicals that could form complexes or precipitates with metal cations, including Na3Cit, EDTA, and Na2HPO4, could lead to a more negatively charged bitumen surface compared with NaCl at pH 8.5. Through analyzing the metal content in the aqueous phase, we proved that ligands promoted the release of metal ions from bitumen, which recovered the negative charges of natural surfactants. Meanwhile, the ligands were capable of adsorbing on bitumen surfaces through outer-sphere and inner-sphere complexation, thus making the bitumen/water interface more negatively charged.<br>
The DFA was applied to study the effect of viscosity on the dynamic film drainage process of: (1) silicone oil interaction with a hydrophilic mica surface and (2) bitumen drop interaction with a hydrophobic silica surface. In system (1), we illustrated that the competition between the viscous normal stress and the Laplace pressure controlled the film drainage process between a very viscous oil drop and a mica surface. The initial height of dimple formation was well captured by a derived analytical formula, h<em>d=0.5R√(〖Ca〗</em>f⁄((1+2〖Ca〗<em>d))), which holds for a wide range of drop capillary numbers. It has been proved that the viscous effect needs to be taken into consideration when 〖Ca〗</em>d&gt;0.1 (〖Ca〗_d, drop capillary number). By applying this formula in system (2), the effect of solvent addition, approach velocity, and temperature on the film drainage process between a bitumen with high viscosity and a hydrophobic silica surface were studied. The results proved that the solvent addition and temperature did not affect the initial stage of dimple formation, and the viscosity was the dominant controlling factor. The formula could also predict the initial height of dimple formation in this complicated bitumen system with a hydrophobic surface. In addition, the attachment time of bitumen onto the hydrophobic surface was found to affect by approaching velocity, interfacial tension, and bitumen viscosity. <br>
By applying the two techniques, a systematic study on the dynamic interaction between various components involved in the oil sands extraction process was performed. The effect of the water chemistry, oil viscosity, approach velocity, and surface hydrophobicity on the drainage dynamics of thin liquid films and surface forces provided fundamental insights into the interaction mechanisms of air bubble/oil drops and solid surfaces. It also provided fundamental understanding for the industrial processes (such as oil sands extraction process, 3D-printing, wastewater treatment and so on) in which oil drops with high viscosity are involved.</p>