Effect of microwave irradiation on the viscosity of crude oil: A view at the molecular level

The increase in global energy demand and decrease in easily extractable light crude oil has generated a growing interest in heavy oil exploitation. However, the high viscosity of heavy oil leads to exploitation, transportation and refining challenges. In this context, microwave irradiation of crude oil samples from Sudan, China (Liaohe) and Venezuela were carried out to investigate the mechanisms of viscosity reduction. Saturate, aromatic, resin, and asphaltene (SARA) analysis of the crude oils was conducted according to the American Society Test and Materials standard, ASTM D4124-09. The SARA fractionation results demonstrated that microwave irradiation may affect the structure of resin/asphaltene micelles, thus leading to a change in the viscosity of the crude oil. The crude oils were further examined using the combined analytical techniques of electrospray ionization and Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results from ESI FT-ICR MS analysis demonstrated that microwave irradiation of crude oil with a high proportion of O2 compounds leads to polymerization, and ultimately an increase in the viscosity of the crude oil after microwave treatment. In other cases, cracking might occur due to the microwave heating.