Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article Facilitating the transportation of highly viscous oil by aqueous foam injection Jiaqiang Jing a,c ,JieSun a,b, ⁎ , Hongbing Huang d ,MingZhang e , Chunsheng Wang e , Xingchang Xue f , Amos Ullmann b , Neima Brauner b, ⁎ a School of Oil & Natural Gas Engineering, Southwest Petroleum University, Chengdu 610500, China b School of Mechanical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel c Oil & Gas Fire Protection Key Laboratory of Sichuan Province, Chengdu 611731, China d Yanchang Oilfield Co. Ltd., Yanan 716000, China e China National Offshore Oil Corporation (CNOOC) Research Institute, Beijing 100027, China f Engineering Technology Research Institute, Xinjiang Oilfield Company, Karamay 834000, China ARTICLEINFO Keywords: High-viscosity oil Aqueous foam Drag reduction Eccentric core fow Stratifed fow Non-Newtonian Two-fuid models ABSTRACT This work aims at studying a new idea for cold transportation of high-viscosity oil by foam injection. Special attentionispaidtothedragreductionachievedbyintroducinganon-NewtonianaqueousfoamtoNewtonianoil inthestratifedandcoreannular fow (CAF) regimes. Pressure gradients were measured during the co-current fowofhighlyviscousoilandfoaminahorizontalrough-walltemperedborosilicateglasspipewith25mintotal lengthand25mminnerdiameter.Measurementsweremadeforoilandfoamsuperfcialvelocitiesintherange of0.1–0.9m/sand0.05–0.84m/s,respectively.Newhydraulicmodelsforfoam-oilhorizontalpipe fow based on the one-dimensional two-fuid approach were established. These models are capable of representing the observedfowconfgurationsranging fromstratifed fowtoconcentricCAFandeccentricCAF.Goodagreement was obtained between the predictions and experimental data over a wide range of operating conditions. A maximum drag reduction ratio could be reached at the critical input foam-to-oil fow ratio, where complete encapsulationoftheoilcorebythefoambecomesfeasible.Anoptimumcore-to-piperadiusratiorangeforthe highest oil-transport operational coefcient was identifed. 1. Introduction Continuous development of the global economy leads to an ever- increasing energy demand. As the worldwide production of conven- tional crude oil has almost reached its peak [1], unconventional oil (heavy and extra-heavy oils), whose reserves double those of conven- tional oils [2], will play a signifcant role over the next two decades [3–4].However,itsspecialphysicochemicalproperties,includinghigh density,highviscosityorpoorfuidity,andhigh fractionofasphaltenes and resins with large molecules bring a huge challenge for heavy oil production [5–8]. Various approaches for heavy oil transportation are mainly achieved by conventional viscosity reduction, like heating [9], dilution [10,11], upgrading [12] and emulsifcation [13] etc., or drag reduction, like core-annular fow [14] and drag reducing additives [15]. Drag reduction methods for high viscosity oil transport were widely considered since these feasible means may practically preserve the oil physical properties and signifcantly save pumping energy [16,17]. Considering the well-known core-annular fow (CAF) for heavy oil transportation by using water as a lubricant, breakup of water flm, emulsifcationofoil/watermixturesandhighwaterconsumptionhave not been efectively solved yet. Consequently, this technology has not reached the level of popularization and application so far [18,19]. Basedonthedragreductionmechanismofmicrobubblesforwall fow encountered in the ship industry and water annulus for transporting heavy oil [20], Jing et al. [21] proposed a new idea to lubricate the viscous oil fow by an aqueous foam annulus instead of a water flm. The advantage of the foam annulus over a water annulus is twofold. First, the foam annulus can completely encapsulate the oil core before excessivedrainingofthefoammaytakeplace.Whenitstartstodrain, the bubbles migrate upward along the pipe wall, while the rest of the foamdrainage fowsdownasaliquidtothelowerpartofthepipedue to the density diference between the bubbles, oil and the draining li- quid. This probably results in a complex isolating-lubricating annulus https://doi.org/10.1016/j.fuel.2019.03.116 Received 22 October 2018; Received in revised form 26 February 2019; Accepted 21 March 2019 ⁎ Corresponding authors at: Southwest Petroleum University, Chengdu 610500, China (J. Sun). E-mail addresses: jjq@swpu.edu.cn (J. Jing), sunj101@163.com (J. Sun), brauner@eng.tau.ac.il (N. Brauner). Fuel 251 (2019) 763–778 0016-2361/ © 2019 Elsevier Ltd. All rights reserved. T