Experimental study on self–emulsification of shale crude oil by natural emulsifiers

Abstract

Self–emulsification can be accomplished by enhanced oil recovery (EOR), the realization of the exploration of natural emulsifiers, which is a crucial task to understand the mechanism of crude oil self–emulsification, albeit it is, of course, accompanied by difficulties, during the development of shale crude oil. In this study, we separated the active components of crude oil, and with the help of modern characterization and laboratory tests, coupled with nuclear magnetic resonance of core flooding method, we fully explored the independent and synergistic effects of crude oil active components, and deepened the understanding of the mechanism of crude oil self–emulsification. Among the active components of crude oil, asphaltene and resin have vital effects on its self–emulsification, which is shown in the amphiphilic structure of asphaltene and the effect of resin solvent. Asphaltene can reduce oil–water interfacial tension to 19 mN/m, and the resin significantly increase the viscosity of emulsion. Meanwhile, resin and asphaltene stabilize the viscoelasticity of oil–water interface films and affect the phase transition of emulsions in different water oil ratio environment. As a result, the active components of crude oil are closely related to formation and stabilization of the emulsion, which together endue the inherent conditions of its self–emulsification. Core flooding test confirmed that some emulsions in nanoscale size are produced in shale porous media, and the average emulsion diameter size is 181 nm. This study explored the effects of natural emulsifiers on the self–emulsification of crude oil, thereby promising new potential opportunities for EOR of shale oil.

Graphical Abstract

Static experiment and core flooding test indicated that asphaltene and resin reduce the oil–water interfacial energy, and aromatic and saturated hydrocarbons stabilize the viscoelasticity of the oil–water interface to synergestically produce nanoscale emlusions in shale porous media.

Keywords:

• Shale oil
• self–emulsification
• crude oil active components
• enhanced oil recovery

Acknowledgment

We acknowledge National Natural Science Foundation of China (Grant Nos. 42172347, U19B2010) for providing financial supports of this study.