Abstract
Abstract To ensure the efficient operation of crude oil dehydration and sewage treatment technology in oilfield surface production system, the effect mechanism of polar components represented by asphaltene and resin on the formation and stability of oil-water emulsion needs to be revealed at nanoscale. In this paper, the molecular dynamics simulation method was used to construct the crude oil/polar component/water system models with different molar ratios of asphaltene to resin by adjusting the number of asphaltene and resin molecules, so as to reveal the molecular arrangement and aggregation process and film forming characteristics of asphaltene, resin, and their mixture at the oil-water interface. The simulated results showed that the aggregation process of asphaltene molecules under the influence of hydrogen bonds can be divided into three stages. The addition of resin molecules enhanced the connection between molecules of all polar components at the interface. The π−π stacking and T-shaped stacking structures were found in all aggregations, and the higher the molar ratio of asphaltene molecules, the higher the proportion of π−π stacking structure. With the increase of the molar ratio of asphaltene to resin increases from 0 : 1 to 1 : 0, the interfacial film thickness and interface formation energy increase from 2.366 nm and -143.89 kJ/mol to 3.796 nm and -304.09 kJ/mol, respectively, which indicated that asphaltene molecules play a more significant role in promoting the formation of interfacial film and maintaining its structural stability than resin molecules. The investigations in this study provide theoretical support for demulsification of the crude oil emulsion.
Highlights
The adjustment and optimization of the global energy structure have decreased the rate of traditional fossil energy demand growth, the oil demand of major developing countries is still increasing, which makes oil recovery enhancement an important direction of oil field development and construction [1]
The chemical flooding technology represented by alkali/surfactant/polymer (ASP) flooding has been applied in Daqing oilfield as an efficient enhanced oil recovery method [2,3,4], while the chemical agent components such as surfactant and polymer will affect the stability of crude oil emulsion, which will bring challenges to the efficient oilwater separation of oilfield gathering and transportation system [2, 4,5,6,7,8,9]
The results showed that only a small part of asphaltenes could play the role of emulsion stability
Summary
The adjustment and optimization of the global energy structure have decreased the rate of traditional fossil energy demand growth, the oil demand of major developing countries is still increasing, which makes oil recovery enhancement an important direction of oil field development and construction [1]. The results showed that only a small part of asphaltenes could play the role of emulsion stability These asphaltenes are generally rich in heteroatomic functional groups and have large molecular weight, which are easy to aggregate and form aggregates. There is still a lack of research on resins, especially the lack of considering the effect of the change of molecular ratio of asphaltene to resin on the aggregation structure, and the arrangement, aggregation behavior, and film forming evolution process of them and their self-assembly structure at the oil-water interface are not yet described in detail. Molecular density distribution, radial distribution function, and interface formation energy were used to describe the alignment, aggregation, and film forming process of asphaltene, resin molecules, and their self-assembly structures at the crude oil water interface, and the effect of molar ratio of asphaltene to resin on film thickness and structural strength was revealed. The investigations in this study can provide theoretical support for demulsification of crude oil emulsion
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