ACESAdvances in Chemical Engineering and Science2160-0392Scientific Research Publishing10.4236/aces.2013.31002ACES-26466ArticlesChemistry&Materials Science Numerical Analysis of Heavy Oil-Water Flow and Leak Detection in Vertical Pipeline oãoVictor Nunes de Sousa1*CristianeHolanda Sodré2AntonioGilson Barbosa de Lima3SeverinoRodrigues de Farias Neto4Department of Mechanical Engineering, Center of Sciences and Technology,Federal University of Campina Grande, Campina Grande, BrazilDepartment of Chemical Engineering, Center of Sciences and Technology, Federal University of Campina Grande, Campina Grande, BrazilDepartment of Chemical Engineering, Technology Center, Federal University of Alagoas, Maceió, BrazilDepartment of Mechanical Engineering, Center of Sciences and Technology, Federal University of Campina Grande, Campina Grande, Brazil* E-mail:joao.vns@hotmail.com(OVNDS);110120130301915September 3, 2012October 5, 2012 October 14, 2012© Copyright 2014 by authors and Scientific Research Publishing Inc. 2014This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/

Pipeline is a conventional, efficient and economic way for oil transportations. The use of a good system for detecting and locating leaks in pipeline contribute significantly to operational safety and cost saving in petroleum industry. This paper aims to study the heavy oil-water flow in vertical ducts including leakage. A transient numerical analysis, using the ANSYS-CFX? 11.0 commercial software is performed. The mathematical modeling considers the effect of drag and gravitational forces between the phases and turbulent flow. Mass flow rate of the phases in the leaking orifice, the pressure drop as a function of the time and the velocity distributions are presented and discussed. We can conclude that volumetric fraction of phases and fluid mixture velocity affect pressure drop and mass flow rate at the leak hole.

Heavy Oil; Multiphase Flow; Leakage; Numerical Simulation1. Introduction

The activity of oil production is subject to high risks. Even the petroleum industry running preventive measures, there is always the possibility of failure, making the industrial plants susceptible to operational accidents with loss of fluid to environment, causing great ecological, social and economic damages, with delay in oil production. A proper supervisory system must be capable of detecting leaks in oil installations, enabling immediate action to reduce the impacts of accidents and contributing significantly to operational safety. The simultaneous flow of two immiscible liquids in vertical pipes is encountered in different industrials processes and particularly in the petroleum industry [1].

Because of importance, many authors have focused their researches in methods of leak detection in pipes on oil production and transport [2-4].

However, in different applications, including oil transportation, accurate locations of the leaks is still very difficult. In present day various leak detection techniques based in the negative pressure wave, acoustic sensors, satellite surveillance, mass and volume balance, analytical model-based method, among others, has been applied. All these methods are based in process variables such as pressure, mass and volumetric flow rates and temperature [5].

According to Dong et al. [6], the negative pressure method, which supplies high leak sensitivity and availability, is a relatively better method among them. Unfortunately this method has a high possibility of false alarm if there are some strong raises in the pressure measurement records or if the leak is small (0.5% of nominal flow) [4,5].

Thus, this paper aims to numerically study the hydrodynamic of heavy oil-water flow in a vertical pipe having a small leak, which is much more difficult to detect by conventional systems [7]. The interest in heavy oil is in fact that recent studies indicate that in 2025 this kind of oil will be the main source of fossil energy in the world [8].

2. Methodology2.1. The Geometry and Grid

The study domain (Figure 1) consists of a vertical pipe with 800 cm (8 m) of length, with a constant circular section 15 cm diameter. To simulate the leakage, the pipe has a circular hole, with 0.6 cm diameter, located at the midpoint of the length of pipe.

Figure 2 illustrates the mesh representing the study domain, which was built with the support of ICEMCFD® 11.0 software. This structured mesh was obtained after various refinements, and it has 327,327 hexahedral elements.

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