An environmentally friendly and commercially available polymer, ethylcellulose (EC), was found to be effective for water removal from water-in-diluted-bitumen emulsions. In a previous study, atomic force microscopy images of bitumen films transferred from the water–toluene interface onto a silicon wafer revealed progressive disruption of bitumen films by increasing the addition of EC. The in situ micropipet experiments, on the other hand, demonstrated the flocculation and enhanced coalescence of two approaching water droplets at low and high EC concentrations, respectively. In this study, we investigated the effect of EC addition on compressibility, composition, thickness, and surface properties of the interfacial films formed by surface-active components of bitumen, aiming to understand the interfacial behavior of EC at the water–diluted bitumen interface. The pressure–area isotherms of Langmuir interfacial films indicated a transformation of a rigid interfacial film formed by surface-active components of bitumen to become much more compressible in the presence of EC. The polarized infrared spectroscopy analysis of the Langmuir–Blodgett (LB) interfacial films proved the adsorption of EC at the water–oil interface, while the thickness measurement of the film indicated the displacement of interfacially active materials by EC. The thickness and contact angle measurements of LB interfacial films revealed an irreversible nature of EC adsorption at the interface. In conclusion, EC is able to irreversibly displace/disrupt the interfacial film formed by surface-active components of bitumen at the water–oil interface and increase the compressibility of the interfacial film, promoting the coalescence of water droplets.

Ethylcellulose (EC) polymers with different hydroxyl content and molecular weight were synthesized in tetrabutyl ammonium fluoride/dimethyl sulfoxide medium. Their performance for demulsification of water-in-naphtha diluted bitumen emulsions was evaluated. It was found that EC with 4.5 wt % hydroxyl (degree of hydroxyl substitution, 2.4) is the most effective in demulsification. The demulsification efficiency of EC could be linked to its interfacial activity and potency of flocculation. The potency of flocculation by EC depends on its molecular weight and hydroxyl content, which affect molecular interactions. EC with higher molecular weight was found to be more effective in the demulsification of water-in-naphtha diluted bitumen emulsions.

A major drawback associated with current hot or warm water-based bitumen extraction processes is the high consumption of energy. To address this issue, an aqueous–nonaqueous hybrid bitumen extraction process (HBEP), in which a portion of the diluent (solvent) was added upfront to soak mined oil sands prior to its water-based extraction, was proposed and demonstrated to be feasible to process mineable oil sands at ambient temperatures. This study investigates the effect of adding ethyl cellulose (EC) as a promising demulsifier to the solvent on bitumen recovery and froth quality in the ambient HBEP. The laboratory flotation results clearly showed a significant improvement in froth quality with a negligible setback on bitumen recovery by 100–200 ppm EC addition to the HBEP. Determined by an online visualization method, the addition of EC in solvent to the HBEP was found to further enhance separation kinetics of bitumen from sand grains of real oil sands ores. The addition of EC in solvent also increased the probability of bitumen droplet coalescence determined with a micropipette technique, but hindered the attachment of air bubbles to solvent-soaked bitumen, in particular at high EC dosages as evaluated by increased induction time of air bubble-bitumen attachment.

There have been numerous laboratory experimental studies and field tests on ASP flooding. Most of the laboratory experiments focused mainly on the effect of the ultra-low oil-water interfacial tension on oil recovery. The relationship between the viscosity of the ASP solution and oil recovery efficiency of ASP flooding has not been well understood. In this paper, the relationship between the viscosity of an ASP solution and oil recovery in heterogeneous porous models was studied. More than 50 ASP flood tests were conducted using artificial models. These models were made to have different permeability variation coefficients so that ASP floods in homogeneous and heterogeneous reservoirs could be simulated. Sixteen ASP solutions were prepared and used in ASP flood tests. Based on the results of ASP flood tests, the effects on tertiary oil recovery of NaOH concentration and of the balance between the IFT reduction and viscosity increase were discussed. For heterogeneous models, it was found that there existed a minimum viscosity value of ASP solution for ultra-low IFT systems to fully work towards improving residual oil recovery. This minimum viscosity is defined as critical displacement viscosity in this study. When the viscosity of an ASP solution is lower than the critical displacement viscosity, the oil recovery efficiency of ASP flooding is dominated by the viscosity of the ASP solution. The reduction in interfacial tension to an ultra-low level contributed little to oil recovery. When the viscosity is higher than the critical displacement viscosity, both the viscosity and ultra-low IFT contributed to oil recovery. This critical displacement viscosity should be one of the important parameters that can be used to optimize the chemical formula of an ASP flood for a target reservoir. Introduction As a relatively new technology of tertiary oil recovery, alkaline/ surfactant/polymer (ASP) flooding has been studied extensively in last two decades(1–9). ASP flooding enhances oil recovery through two major mechanisms:increasing the viscosity of the displacing solution to improve the sweep efficiency by using polymer; and,reducing oil-water interfacial tension (IFT) to a very low value (~10−3 mN/m) to improve the pore level displacement efficiency through the synergetic effect of surfactant and alkaline(10). Field tests and laboratory studies have shown that ASP flooding is more efficient than any single component flooding, such as alkaline, surfactant, or polymer flooding(6–8). At present, it is a promising tertiary recovery method and is getting increasingly more attention. Seven field ASP floods have been implemented in the Daqing oilfield, China. It was found that in the early stage of some tests high alkaline concentrations could cause alkaline scale problems in he oil formation and the wellbore(8, 9, 11). In addition, high alkaline concentrations could weaken the efficiency of the polymer by increasing the viscosity of the ASP solution. Therefore, the polymer concentration in some field tests was increased from 1,200 mg/L to 1,800 mg/L, and then to 2,300 mg/L, in order to ensure that the viscosity of the ASP solution was not lower than 30 mPas.

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