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An experimental flow loop was designed and constructed to perform the wax deposition tests under the oil/gas twophase flow conditions in a horizontal pipe. The oil sample came from the Daqing Oilfield of China, which was characterized by high wax content. A particular local sampler was designed and installed at the outlet of the test section in the flow loop to make up for the drawback of no visual observation during the course of flow pattern verification, which is a good device to help verify the flow pattern by analyzing the inner flow situations at different circumferential and vertical positions. Using the local sampler in combination with analyzing the changes in pressure drop and liquid holdup, which is defined as the fraction of an element of pipe occupied by liquid at the same instant, flow patterns were identified and divided into two main categories, namely, the stratified flow and slug flow. Wax deposition tests were selected in the definite flow pattern regions instead of flow pattern transition regions. The effects of flow pattern characteristics on wax deposition were experimentally studied under the oil/gas two-phase flow conditions. The results show that liquid superficial velocity, gas superficial velocity, shear stress at the liquidÀdeposit interface, liquid holdup, and slug frequency do play an important role in wax deposition in the oil/gas two-phase flow. The wax deposition characteristics were experimentally obtained for stratified flow and slug flow. The experimental results in this study provide an experimental reference and insight for further study on wax deposition in multiphase flow, especially under the conditions that the oil sample is characterized by high wax content.' EXPERIMENTAL SECTION Experimental Sample. The experimental oil sample used in the study was a typical waxy crude oil characterized by high wax content and

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Résumé -Dérivation de l'équation d'énergie de l'écoulement huile-gaz dans des pipelines -Lors de la simulation d'un écoulement multiphasique huile-gaz dans une conduite, le calcul thermodynamique représente un processus important en interaction avec le calcul hydraulique ; il influence la convergence du programme et la précision des résultats. La forme de l'équation d'énergie constitue la clef du calcul thermodynamique. Basée sur l'équation d'énergie de l'écoulement huile-gaz dans un pipeline, la formule de chute de température explicite (ETDF ; Explicit Temperature Drop Formula) est dérivée pour un calcul de température d'état stable huile-gaz. Cette nouvelle équation d'énergie prend en compte de nombreux facteurs, tels que l'effet Joule-Thomson, le travail de pression, le travail de frottement, ainsi que l'incidence des ondulations de terrain et le transfert de chaleur avec le milieu extérieur le long de la ligne. Ainsi, il s'agit d'une forme globale de l'équation d'énergie, laquelle pourrait décrire précisément la réalité d'un pipeline à phases multiples. Pour cette raison, un certain nombre de points de vue de la littérature à propos du calcul de température d'un écoulement diphasique huile-gaz dans des pipelines sont passés en revue. L'élimination de la boucle d'itération de température et l'intégration de l'équation de température explicite, au lieu de l'équation d'énergie d'enthalpie, dans le calcul conjugué hydraulique et thermique, se sont avérées améliorer l'efficacité de l'algorithme. Le calcul a été appliqué non seulement au modèle de composants mais aussi au modèle Black-Oil. Ce modèle est incorporé respectivement dans le modèle de composants ainsi que le modèle Black-Oil et deux simulations sont effectuées sur deux pipelines en service, les pipelines multiphasiques Yingmai-Yaha et Lufeng ; les résultats de température sont comparés à la simulation calculée par OLGA et aux résultats mesurés. Il est montré que ce modèle a très bien simulé la distribution de températures. Enfin, on a analysé l'influence de la capacité thermique spécifique du pétrole et du gaz sur la température du mélange des fluides et l'influence de l'effet Joule-Thomson sur la répartition de température sur le pipeline. Il est montré que le coefficient de Joule-Thomson représente un facteur clef pour décrire correctement un écoulement diphasique huile-gaz. Oil & Gas Science and Technology -Rev. IFP Energies nouvelles, Vol. 68 (2013), No. 2, pp. 341-353 Copyright © 2012, IFP Energies nouvelles DOI: 10.2516/ogst/2012020 Oil & Gas Science and Technology -Rev. IFP Energies nouvelles, Vol. 68 (2013 Abstract -Energy Equation Derivation of the Oil-Gas Flow in Pipelines -In the simulation of oil-gas pipeline multiphase flow, thermodynamic computation is an important process interacting with the hydraulic calculation and it influences the convergence of the program and the accuracy of the results. The form of the energy equation is the key to the thermodynamic computation. Based on the energy equation of oil-gas flow in pipeline, the E...

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Wax formation is a serious problem in the gas and oil industry because it can block oil production facilities and transportation pipelines. It is, therefore, of great importance to have a reliable tool to predict wax formation under various operational conditions. The hydrocarbon plus fractions that comprise a significant portion of naturally occurring hydrocarbon fluids create major problems when determining the thermodynamic properties and the volumetric behavior of these fluids by equations of state. In this work, an effort has been made to further improve the characterization of the plus fraction, splitting the plus fraction into a single carbon number (SCN) and generating the mole fraction, on the basis of the relationship between the three-parameter gamma distribution, experimental molar fraction, molecular weight, and SCN data obtained from literature and industrial contact. The three-parameter gamma distribution is used to fit the trend of the computational analysis. The method has been used to predict wax appearance temperatures (WATs) for a great number of systems and to compare with some methods generated previously. The average deviation of the calculated WAT is 1.47 K for the system with the experimental data. There are some correlations generated to calculate the physical-chemical properties as a function of SCN. Those correlations have been originally developed to work with light oil. The developed approach, along with some of the correlations, is tested for calculating WAT to identify the applicability in this work.

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