Journal of Petroleum Science and Engineering xxx (xxxx) xxx Please cite this article as: Lorena A. dos Santos, Journal of Petroleum Science and Engineering, https://doi.org/10.1016/j.petrol.2020.107932 Available online 25 September 2020 0920-4105/© 2020 Elsevier B.V. All rights reserved. Heavy oil transportation through steam heating: An analytical and numerical approach Lorena A. dos Santos a , Daniel da C. Ribeiro a, b , Oldrich J. Romero a, b, * a Graduate Program in Energy, Federal University of Espirito Santo, Sao Mateus, Espirito Santo, Brazil b Engineering and Technology Department, Federal University of Espirito Santo, Sao Mateus, Espirito Santo, Brazil A R T I C L E INFO Keywords: Viscous oils Concentric steam pipe Heat transfer Steam quality Flow assurance ABSTRACT Amongst the innumerable challenges that permeate the production chain of heavy oils, the transportation stage deserves to be highlighted. Due to its high viscosity, heavy oils exhibit considerable fow resistance, requiring auxiliary mechanisms to enable its transportation via pipelines. This study analyzes a concentric pipeline confguration, in which steam fows through the inner pipe and oil fows through the annular space of the oil pipe. The main goal is to investigate the impacts of steam insertion, concentric coupling dimensions, thermal insulation, steam quality and system horizontal length on the main parameters of fow control: oil temperature and viscosity. As a secondary parameter, oil initial pressure required to ensure fow completion is also discussed. In this intent, a numerical approach is applied with software Ansys CFX in a tridimensional, steady state simulation. A second objective is to estimate the main parameters of interest by an analytical approach, using the thermal resistance model associated with the ε – NTU method. The goal is to determine if, given a similar coupling scenario and the absence of computational resources, oil temperature and viscosity can be estimated by direct calculations within an acceptable range of deviation from the numerical approach. Heat transfer rates are also estimated as secondary parameters. Numerical results for a 1-m length system reveal that steam insertion elevates the average oil temperature in 1.2%, reducing its average viscosity and initial fow pressure by 8.7% and 24.2%, respectively. From the previous scenario, a reduction of 24.6% in the oil pipe/steam pipe radius ratio results in an additional 1.2% temperature increase and 4.7% viscosity reduction. On the other hand, reducing steam quality in 30% implicates an average oil viscosity 2.4% higher. In a 4-m system, a convective cell pattern is observed, in which oil heating and viscosity reduction reaches its peak at the central upper region of the annular space, highlighting cooler and denser deposits in the lower section of the system and a nonlinear heating process. Maximum deviations between numerical and analytical approaches in oil temperature and viscosity estimates are 1.3% and 15.6%, respectively, which indicate the latter as a suitable calculation method for small systems in the absence of numerical resources. Deviations are mainly attributed to the neglect of natural convection, gravita- tional and steam turbulence effects, which contribute for a non-homogeneous heating of oil. 1. Introduction According to data from the International Energy Agency – IEA (IEA, 2016), it is estimated that in 2014 the oil world demand has increased in 1.4% when compared to 2013. In 2015, oil production has increased in 3% when compared to the previous year, reaching the mark of 94.2 million barrels per day. This increase is attributed, in larger scale, to the United States (+7.8%), Saudi Arabia (+5.8%), Iraq (+13.8%) and Brazil (+7.7%). In this context, efforts have been applied in the research and devel- opment of new energetic sources. In Brazil, such options include, but are not limited to: solar, wind and hydraulic energy, ethanol and biodiesel (Pereira et al., 2012). However, alternative sources proposals for the diversifcation of the energetic matrix are relatively recent when compared to the usage of fossil fuels such as petroleum, natural gas and charcoal (Sen and Ganguly, 2017). Conventional oils, located in highly porous and permeable reser- voirs, whose extraction requires minimal stimulation techniques, are continuously rarer. On the other hand, the expressive volume available of non-conventional oils has awakened the industry interest (Phaf et al., 2013), which include oily sands and heavy oils. The high viscosity of heavy crude oil makes the fows through a reservoir very slow and the wells produce at lower rates than light oil wells (Sami et al., 2017; da * Corresponding author. Graduate Program in Energy, Federal University of Espirito Santo, Sao Mateus, Espirito Santo, Brazil. E-mail addresses: lorenaandrade56@hotmail.com (L. A. dos Santos), daniel.ribeiro@ufes.br (D. da C. Ribeiro), oldrich.romero@ufes.br (O.J. Romero). Contents lists available at ScienceDirect Journal of Petroleum Science and Engineering journal homepage: http://www.elsevier.com/locate/petrol https://doi.org/10.1016/j.petrol.2020.107932 Received 31 December 2019; Received in revised form 19 August 2020; Accepted 10 September 2020