Small Sizes of Molybdenum Disulfide Nanosheets As Heavy Oil Viscosity Reducers

The high content of asphaltenes and colloids in heavy oil lead to their high viscosity, making it difficult to exploit and transport. Nanomaterials have become an important additive in reducing viscosity of crude oil. In this work, a series of amphiphilic molybdenum dioxide (MoS₂) nanosheets are developed to reduce the viscosity of crude oil by an ultralow concentration aqueous solution.

Firstly, nanosheets were synthesized by the hydrothermal methods. The influence factors such as raw material ratio, temperature and time were investigated. Then, SEM are used to systemically characterize the morphology and structure of MoS₂ nanosheets. Then, the properties (i.e., size, viscosity reduction, and interfacial activity) of MoS₂ nanosheets are tested. The relationship between these properties and viscosity reduction abilities were studied. Finally, based on viscosity reduction testing results, optimal MoS₂ nanosheets formulation and dosage are determined.

By controlling the stirring and temperature, hydrophilic MoS₂ nanosheets with sizes from 40 nm to 160 nm were synthesized, respectively. Modifying them with oleyl amine, the amphiphilic nanosheets can be obtained. SEM show that they are materials with layered nano-structure and commonly composed of 8–10 layers. These nanosheets have good interfacial activity, wetting and emulsifying ability. By adding 100 ppm of MoS₂ nanosheets to the mixture of heavy oil and water, the viscosity of these system can fall from > 880 mPa·s to 9 mPa·s. The smaller the size of the MoS₂ nanosheets is, the better the viscosity reduction ability will be. The optimal using dosage of these nanosheets is 300–400 ppm, and the optimal size is 40–60 nm. It is predicted that nanosheets will gradually become a new field for the development of heavy oil.