The increasing world oil demand has led to develop the large heavy and extra heavy oil resources located in Venezuela. Heavy oil production and transportation are especially difficult due to the high viscosities of this oil that increase the complexity of the multiphase flow involved. Traditionally, low/gas liquid ratios have been associated to heavy and extra heavy oil fields; however, the experiences in the Faja Petrolífera del Orinoco Hugo Chávez Frías (FPO-HCF) indicate the presence of enough volumes of gas that impose further technical challenges which must be considered in surface facility processes – to be able to handle multiphase flow, and the different flow patterns that could be promoted through pipelines.

In the case of heavy and extra heavy oil fields, hydrodynamic slug flow is the most common flow pattern. For this reason, it is important to know how this flow pattern behaves as oil viscosity increases in order to improve the operation and design of surface facilities, such as: pipelines, separators, flow conditioners, risers, multiphase equipment, etc. Additionally, if slug flow pattern is better understood, corrosion effects could be better predicted, therefore, strategies to reduce this problem will be considered in a rigorous way.

One of the approaches to understand the slug flow pattern is experiments and improved mathematical models that predict both the flow pattern transitions and the slug flow characteristics. To this end, an experimental study of three different gas/liquid systems is made which includes liquid viscosities of 0.001 Pa.s, 0.418 Pa.s, and 0.996 Pa.s. In this work was studied the liquid viscosity effect on the slug flow characteristics, such as: flow pattern transition, slug translational velocities, slug lengths, pressure drops, holdup, and slug frequency. Moreover, a flow pattern transition model is proposed for two-phase gas highly viscous liquid systems.


By early 2014, Venezuela had nearly 298 billion barrels of proved oil reserves, the largest in the world. Most of these vast resources are heavy and extra heavy oils located in the FPO-HCF.

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