Heavy crude oil viscosity reduction and rheology for pipeline transportation Shadi W. Hasan a , Mamdouh T. Ghannam b, * , Nabil Esmail a a Department of Mechanical and Industrial Engineering, Concordia University, Montreal, Quebec, Canada b Department of Chemical and Petroleum Engineering, College of Engineering, United Arab Emirates University, Al-Ain, United Arab Emirates article info Article history: Received 3 December 2008 Received in revised form 25 May 2009 Accepted 15 December 2009 Available online 5 January 2010 Keywords: Heavy crude oil Viscosity reduction Oil/water emulsion Alcohol Yield stress abstract Different methods of reducing the viscosity of heavy crude oil to enhance the flow properties were inves- tigated. Experimental measurements were conducted using RheoStress RS100 from Haake. Several fac- tors such as shear rate, temperature and light oil concentration on the viscosity behavior have been studied. This study shows that the blending of the heavy crude oil with a limited amount of lighter crude oil provided better performance than the other alternatives. Experimental measurements in terms of shear stress s–shear rate _ c; and yield stress s 0 were conducted on the mixture of heavy crude oil–light crude oil (O-light). The results showed a significant viscosity reduction of 375 mPa s at a room temper- ature of 25 °C. This study shows that the heavy crude oil required a yield stress of 0.7 Pa, whereas no yield stress was reported for the heavy crude oil–light crude oil mixture. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Crude oil is one of the most actively traded commodities in the world. Oil prices change daily in response to fluctuating conditions that affect supply and demand. Global demand for crude oil has been intensifying steadily over the past 20 years, as world demand for crude has grown from 60 million barrels per day to 84 million barrels per day. The market price for heavy crude oil is only about one-half that of light crude oil, which is the price generally quoted by the media. Oil transportation has become a complex and highly technical operation. One of the major difficulties in the pipeline transporta- tion is the high viscous fluids that require efficient and economical ways to transfer the heavy crude. Heavy crude oils have a density approaching or even exceeding that of water. They are usually ex- tremely viscous, with a consistency ranging from that of heavy molasses to a solid at room temperature. Heavy crude oils are not pumped easily through the pipelines because of the high con- centrations of sulfur and several metals, particularly nickel and vanadium. Crude oils are complex fluids that can cause a variety of difficulties during the production, separation, transportation and refining of oil [1,2]. The formation of emulsion is another problem that occurs in the petroleum industry. Indeed, crude oil is often mixed with water when it comes out from a well. As the oil–water mixture passes over chokes and valves, mechanical input leads to the formation of water-in-oil (W/O) emulsions [3–5]. Such emulsions are consid- ered as a ruthless problem within the petroleum industry due to their various costly problems in terms of production loss and trans- port difficulties. Heavy crudes account for a large fraction of the world’s potentially recoverable oil reserves. The viscosities of those crudes at room temperature vary from 100 mPa s to more than 10 5 mPa s. Generally, crude oil with viscosity <400 mPa s is the classical maximum desired pipeline viscosity [6–8]. Therefore, different methods are used in order to reduce the vis- cosity of the heavy crude for the pipeline transportation. For in- stance, dilution with lighter crudes or alcohols, heating, and the use of surfactants to stabilize emulsions are some of those com- mon methods. Heating is a common method utilized to overcome the above noted problems of transporting heavy oil by pipeline [1]. The basis for this method lies in the fact that as heavy oil is heated, the viscosity of the heavy oil is reduced and thus made easier to pump. Therefore it is important to heat the oil to a point where the oil has a substantially reduced viscosity. A principle drawback to the use of heated pipelines is the high capital and operational cost of such a heated pipeline over long distances [9]. In addition, underwater pipeline transportation of heavy oil through a heated pipeline is very difficult due to the cooling effect of the surround- ing water and the practical difficulty of maintaining pumping sta- tions and heating stations [10,11]. Another method utilized in the transportation of heavy crude oil is the formation of the emulsions [12,13]. In such a method the heavy oil is suspended as micro-spheres stabilized in a water continuous phase by the use of surfactants and detergents forming an O/W emulsion, and thus achieving a reduction in the apparent 0016-2361/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2009.12.021 * Corresponding author. E-mail address: mamdouh.ghannam@uaeu.ac.ae (M.T. Ghannam). Fuel 89 (2010) 1095–1100 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel