Heavy oil is defined as petroleum whose density is less than 20API. When its density is less than 10API, it’s called ultra heavy crude oil (UHCO) or bitumen. Due to the shortage of petroleum all over the world, UHCO are getting more and more attentions. But the difficulties of heavier density, higher viscosity and worse fluidity are faced during the production and transportation of UHCO.
The formation of oil in water emulsions with the help of surfactant agents is an effective way to reduce the viscosity of UHCO. It can be obtained by shaking, stirring or some other kind of intensive dynamic and /or static mixing processes. To avoid phase separation, surfactants and stabilizing agents are added to reduce oil interfacial tension. But the stability of the emulsions depends on many factors such as the composition of UHCO, surface active molecules, type of surfactants and their concentration, energy in mixing, size of the droplets, salinity and PH of water and temperature etc.
Researchers from the Institute of Acoustics, Chinese Academy of Sciences propose a method to improve the stability of oil in water (O/W) emulsions for Fengcheng UHCO with the addtion of surfactant agents by using of ultrasonic wave which is produced with the piezoelectrical and/or hydrodynamic acoustic sources.
According to the experiments, the effects of ultrasonic wave on the viscosity reduction for Fengcheng O/W viscosity reduction with different percentage viscosity reducer are active. A decrease of more than 25% viscosity for the O/W viscosity reduction is achieved. Meanwhile, 30% less quantity of viscosity reducer is needed (See Fig.1). In addition, the emulsion with UP is more uniform and stable.
The optimal such as ultrasonics procession (UP) time and electrical power input can be chosen for the special situation. There is an optimal situation such as UP time, electrical power input, and the concentration of the emulsion for UP. Before the UP is used to pilot test in the oil field, experiments must be done to choose the optimal situation.
Cautions must be taken when the oil droplets whose diameter is less than 10μm forms, it does harm to pipelining because such small oil droplets can increase the viscosity of the oil in water emulsion and cause emulsion inversion to water in oil. The viscosity of the emulsion will increase sharply when it happens.
Fig.1 Viscosity- temperature of O/W viscosity reduction for different percent viscosity reducers (Image by XU).
References:
XU Delong, DENG Jingjun, LI Chao, BAI Lixin, DING Bin and LUO Jianhui. Research on Viscosity Reduction of Oil in Water for Ultra Heavy Oil by Using of Ultrasonic Wave. Proceedings of the 21st International Congress on Sound and Vibration, ISSN2329-3675/ISBN 978-83-62652-66-2, International Institute of Acoustics and Vibration (IIAV), SS24-26, 2014.
Contact:
XU Delong
Laboratory of Ultrasonic Physics and Exploration, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
E-mail: xudelong@mail.ioa.ac.cn